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CDPH Guidance for Local Health Jurisdictions and Community Service Providers for ​Extreme Heat


​Revised August 4, 2023. Guidance subject to change.
Original recommendations released September 8, 2022

​​The purpose of this resource is to provide local health jurisdictions (LHJs) and other community-based service providers recommendations and resources to protect communities from heat-related health impacts, with particular focus on supporting population groups most at risk. ​

If a local health department, or other local or Tribal jurisdiction, has an existing heat emergency, adverse weather, or emergency action plan, consult the existing plan first.​ This CDPH guidance provides additional or supplemental information and guidance, but does not replace your local plans.


​Updates as of August 4, 2023:

  • Added information on using the National Weather Service’s “HeatRisk” forecast tool

  • Updated information on factors that increase risk of heat illness, expanded the list of populations at higher risk, and added new information and resources for protecting specific population groups

  • Included additional resources and tools for local heat safety planning and preparedness

Key Sections:


What Can Be Done to Protect Communities from Extreme Heat?

​As the climate continues to change, California is experiencing more frequent, more severe, and longer-lasting episodes of extreme heat, posing a greater danger to Californians. Heat kills more people directly than any other weather-related hazard,[1] with approximately 1,220 people dying from extreme heat every year in the United States.[2] In California, between 2010-2020, there was an average of more than 5,000 emergency department visits and 60 deaths per year due to heat-related illness.[3​] Certain population groups, such as older adults, infants and children, pregnant people, and people with chronic health conditions can be especially sensitive to heat exposure. These characteristics, combined with existing health inequities and additional factors, such as poverty, type of occupation (e.g., working outdoors or in unconditioned indoor environments), linguistic isolation, housing insecurity, and the legacy of racist redlining policies on neighborhood conditions such as housing, trees, and asphalt can lead to disproportionately high risk of heat-related illness and death.[4​] 

However, heat-related illnesses and deaths are preventable. This guide provides local health jurisdictions (LHJs) and other community-based service providers recommendations and resources to protect communities from heat-related health impacts, with particular focus on supporting population groups most at risk.

Health Effects of Extreme Heat​

Heat-related illnesses (or heat illnesses) include heat rash, sunburn, heat cramps, heat exhaustion, and, most seriously, heat stroke and death. Warning signs of heat-related illnesses vary, but may include heavy sweating, muscle cramps, weakness, headache, nausea or vomiting, paleness, tiredness, or dizziness. Multiple days of extreme high temperatures will make people more vulnerable to heat-related illness. Learn the warning signs and symptoms, and what to do if you or someone you know is suffering from heat-related illness by visiting the Center for Disease Control and Prevention’s (CDC)​ Signs and Symptoms of Heat-Related Illness webpage

Mental Health Impacts. Heat is also a psychological stressor, affecting mental health – with links to mood and anxiety disorders, schizophrenia, vascular dementia, as well as increased use of emergency mental health services, levels of suicide*, interpersonal aggression, and violence.[5​​] Learn more about the mental health impacts of climate change (including from extreme heat) and ways to support mental health by viewing this resource from the American Psychological Association and ecoAmerica: Mental Health and Our Changing Climate: Impacts, Inequities, Responses (PDF)

*If you or someone you know is struggling or in crisis, help is available. Call or text 9-8-8 or chat at 988lifeline.org

Increase Heat Resilience at the Community Level

  • ​​​​​Build resilience to extreme heat at the community level by supporting solutions that can reduce heat risk and heat islands​, strengthen energy grid resilience, and prevent heat-related health impacts from occurring in the first place, with prioritization for neighborhoods and populations facing disproportionate heat risk. Measures include, but are not limited to: 

    • maintaining housing stability and reducing risk of homelessness;

    • improving existing housing conditions;

      • ​​installing passive cooling measures[​6] in homes and buildings (e.g., cool roofs, cool walls, green roofs);

      • ​increasing access to weatherization and energy efficiency services (including energy-efficient cooling equipment and appliances); 

    • ​increasing shade;

      • ​​​planting more trees, including around homes, at schools and community gathering places, and along transportation corridors to provide shade for pedestrians and cyclists; 

      • ​providing more shade structures in public spaces, including at public transit stops (shade can be from trees, structures, or “shade sails”​​); 

    • increasing community green spaces and vegetation, like parks and community gardens;

    • reducing asphalt and other heat-absorbing surfaces, and increasing cool pavements, permeable surfaces, and natural ground cover;

    • increasing access to water resources, including hydration stations and  water fountains; as well as natural water bodies and artificial water features like public swimming pools, splash pads, and misting systems to cool off; and

    • ​developing a local heat emergency or adverse weather action plan or updating existing local emergency action plan to including addressing extreme heat​.

  • ​​​​Learn more about State-level efforts to address extreme heat by viewing the California Extreme Heat State Action Plan (PDF)​

  • ​Also see What Funding Opportunities Are Available to Increase Community Resilience to Extreme Heat?

Plan and Prepare Communities for Extreme Heat

  • ​Utilize available tools to plan and prepare for extreme heat​, including signing up for local weather / heat alerts, and using the National Weather Service’s (NWS) “HeatRisk” forecast tool ​(more information below).​​

  • Share information with communities ahead of hot temperatures about how to stay safe, including sharing resources from: 

Determine Your Community’s Risk of Heat Impacts: ​

  • To find out your location’s heat risk, use the National Weather Service (NWS) HeatRisk forecast tool (see below for a summary of the HeatRisk levels). ​​The forecast can provide advance warning and inform heat safety planning and preparedness before extreme heat occurs.

NWS HeatRisk: Understanding HeatR​​isk.​ 

Source: National Weather Service (NWS). HeatRisk: “Understanding HeatRisk.”

  • ​The CDPH Heat Risk Grid (PDF; see thumbnail / link below) provides general information about the risk of heat-related impacts anticipated, who is at risk, and what actions individuals and households should take to stay safe in the heat at each HeatRisk level listed. It is meant to provide risk guidance for decision makers and heat-sensitive populations. This Grid should be used as a starting point for informing corresponding community-level actions to ​reduce the risk of heat-related illness for populations at risk.

  • ​​For example:

    • ​​​​​​​If the Grid shows a “Moderate” heat risk level (Level 2 / Orange), this may trigger local actions like increasing public outreach and awareness on the health risks of heat and how to manage activities outdoors, how to stay cool when outdoors and indoors, along with activating other community-level or local heat response measures, with particular focus on protecting populations at risk for heat-related illness, to support people staying cool and reducing their heat risk for heat-related impacts.

    • A “Major” heat risk level (Level 3 / Red) may trigger additional local response measures to help ensure community members are able to stay cool and hydrated, including promoting or providing access to locations in the community that are cool or have air conditioning, distributing water, and checking in with heat-vulnerable residents. 

    • An “Extreme” heat risk level (Level 4 / Magenta) may activate the highest level of local response, including widescale actions to expand access to a cool location or one with air conditioning, hydration, and other measures to stay cool, and community watch efforts, such as friends and family regularly checking on each other and scaling up neighborhood measures like performing door-to-door checks on heat-vulnerable populations (if that is not already being done). 

  • ​Each local jurisdiction should determine the necessary and appropriate actions to take based on community needs and local conditions and prioritize actions to protect populations and communities most at risk of ​the health impacts of extreme heat. 

  • For information on assessing priority populations for heat-related outreach or programming in your communities, please see What Other Heat Planning and Response Tools Are Available?​


CDPH Heat Risk Grid (adapted from NWS HeatRisk tool)

​​Click on the CDPH Heat Risk Grid above to view.

The CDPH Heat Risk Grid is adapted from the National Weather Service: Understanding HeatRisk.[7]


​​​What is the “HeatRisk” Forecast and How Do I Use It​?


HeatRisk Forecast

Screenshot of NWS HeatRisk forecast homepage and map. Source: National Weather Service.


​​Identifying Potential Heat Risks in a Seven-Day Forecast​

Information below adapted from the NWS HeatRisk Overview.

​Why Use HeatRisk?

  • HeatRisk is a better indicator than using temperature alone

  • HeatRisk takes into consideration how unusual the heat is for your location and time of the year

  • HeatRisk accounts for how long the heat will last (including both daytime and nighttime temperatures) and for humidity

  • HeatRisk incorporates data from the Centers for Disease Control and Prevention (CDC) to determine if temperatures pose an elevated risk of heat-related health impacts

Understanding the HeatRisk Forecast:

The National Weather Service (NWS) HeatRisk tool is a color-numeric-based index that provides a seven-day forecast of the potential level of risk for heat-related impacts to occur over each day (24-hour period). The latest version of the HeatRisk tool incorporates heat-health data from the Centers for Disease Control and Prevention (CDC) to influence the local thresholds and inform the approach. That level of risk is illustrated by a color/number along with identifying the groups potentially most at risk at that level. Each HeatRisk level is also accompanied by recommendations for heat protection and can serve as a useful tool for planning for upcoming heat and its associated potential risk. Based on the NWS high resolution national gridded forecast database, a daily HeatRisk value is calculated for each location from the current date through seven days in the future. The National Weather Service uses this tool plus their expert judgement to declare heat advisories, watches, and warnings.

This HeatRisk tool can be used to protect lives and property from the potential risks of excessive heat, and may be especially useful for those who are more easily affected by heat or those who provide support to heat-vulnerable individuals. Weather extremes generally affect historically underserved and marginalized communities the most, and the HeatRisk forecast service ensures that communities have the right information at the right time to be better prepared for ​upcoming extreme heat.

How to Access the HeatRisk Tool:

  • Go to the NWS HeatRisk tool webpage

  • Click the magnifier icon and type in your address or location

  • Once address / location entered, the tool will display a seven-day forecast starting with the current day, including high and low temperatures, and potential heat risk (with HeatRisk levels indicated by the colors green / yellow / orange / red / magenta). Additionally, information about hazardous weather conditions will be provided (for example, excessive heat warnings). See example screenshot for Sacramento, California below during the September 2022 heat wave:​

NWS HeatRisk forecast, Sacramento, California. Accessed September 4, 2022.

NWS HeatRisk forecast, Sacramento, California. Accessed September 4, 2022.


The HeatRisk tool also provides additional decision-support layers (see the “layers” icon at the upper right of the map) that allow users to view geographic boundaries (including US Counties and Tribal Lands), other NWS heat information (i.e., Heat Advisory, Excessive Heat Watch or Warning), and social vulnerability (based on the CDC / ATSDR Social Vulnerability Index) as an overlay layer.

HeatRisk map showing US County boundaries and Social Vulnerability Index overlay. Accessed June 26, 2023.

HeatRisk map showing Social Vulnerability Index (SVI) overlay. Accessed June 29, 2023.​​


​​What Factors Increase the Risk of Heat-Related Illness?

  • Personal factors. Age, obesity, dehydration, heart disease[8​], mental health conditions​, poor circulation, sunburn, pregnancy, and prescription drug and alcohol use all can play a role in whether a person can cool off enough in very hot weather.

  • Exertion level. Even young and healthy people can get sick from the heat if they participate in strenuous[9] physical activities such as Physical Education during hot weather without gradually acclimatizing to hot conditions over a period of 1–2 weeks.

  • High humidity. When the humidity is high, sweat won’t evaporate as quickly. Evaporation of sweat is the main way the body can cool itself.​

​Who is most at risk to health effects of heat?

​​Extreme heat can affect anyone, but those with greater heat sensitivity or heat vulnerability are at an increased risk of heat illness and death. In many cases, there can be multiple and/or simultaneous factors affecting someone that increase their overall risk and vulnerability to heat-related health impacts. For example, someone can be unhoused (or live in a single room occupancy / SRO unit), work outdoors as an agricultural worker, have a chronic health condition, and have limited English proficiency – all factors that can contribute to the cumulative risk of heat illness and death. 

In general, populations at greater risk of heat-related health impacts include (but are not limited to) those who:​

  • Are unhoused

  • Are in particular age groups, such as older adults or infants and very young children

  • Are pregnant (extreme heat is associated with increased risk of preterm birth and stillbirth)

  • Have a disability, have access and functional needs (AFN), or are homebound

  • Are affected by chronic health conditions or other illness

  • Are affected by certain mental health or behavioral health conditions, or substance abuse disorders[10] (including those taking common psychotropic medications (PDF) or use alcohol and other substances – see next item)

  • Are taking certain medications (like antidepressants, beta-blockers and other heart medications) or substances (like alcohol) that can interfere with the body’s internal “thermostat” or impair sweating

  • Work outdoors – especially new workers, temporary workers, or those returning to work after a week or more off (e.g., agricultural workers, construction workers)

  • Work indoors in non-cooled spaces or non-air conditioned environments (e.g., warehouse workers)

  • Work in protective service occupations, including firefighters, police officers, and emergency responders

  • Are exercising or doing strenuous activities outdoors (or indoors in spaces without adequate cooling) during the heat of the day – especially those not used to the level of heat expected, those who are not drinking enough fluids, or those new to that type of activity

  • Live alone or are socially isolated, without others to check on them

  • Live, work, or go to school in urban areas (due to urban heat island effect), particularly areas with more asphalt and dark surfaces, and less shade, tree canopy, or green spaces

  • Live in households without air conditioning, particularly for residents on top floors of multi-story residential buildings; along with those who live in geographic areas where homes historically have not needed air conditioning (for example, coastal communities), or in circumstances where residents cannot afford to run their air conditioning

  • Are incarcerated (for more information, please visit the California Department of Corrections and Rehabilitation’s (CDCR) Extreme Heat Prevention and Response webpage​)

  • Have limited English proficiency (LEP)

  • Use electricity-dependent assistive technology and medical equipment

  • ​Live in mobile or manufactured homes, rental housing, or single room occupancy (SRO) units

  • Otherwise are exposed to heat or the sun, especially long-lasting heat

  • Otherwise lack access and/or mobility options to travel to public cooling facilities, shaded areas, green spaces, or other places with reliable cooling and hydration

  • Otherwise already experience social and health inequities


What Are Specific Actions to Protect Populations at Higher Heat Risk?

​​General Information and Recommendations:

  • For information on protecting specific populations, including older adults aged 65+, infants and children, those with chronic conditions, low-income populations, athletes, outdoor workers, and pregnant people, please refer to the CDC’s “Protecting Disproportionately Affected Populations from Extreme Heat” webpage (en Españ​ol).

  • For general information on protecting people with disabilities in the face of emergencies (including heat emergencies), please refer to the resources available from Re​ady.Gov and the U.S. Environment​al Protection Agency.

  • ​For information on protecting pregnant individuals and babies, please refer to the California Office of Environmental Health Hazard Assessment’s (OEHHA) fact sheet, Pregnancy and Heat – Protect Yourself and Your Baby (PDF).

  • For additional general guidance and tips for ways to stay safe during extreme heat, please refer to the CDPH Extreme Heat homepage or the CDC Extreme Heat homepage.

  • Provide heat-related health education or guidance information in multiple languages to ensure language accessibility. Consider translating and providing outreach in any language exceeding a certain minimum threshold or geographic concentration of individuals that speak that language. For example, the California Department of Health Care Services (DHCS) determines the non-English languages (PDF) in which, at a minimum, Medi-Cal managed care health plans must provide translated written member information (see DHSC-determined Threshold and Concentration Languages for all Counties, as of July 2021).

  • Consider collaborating with other local agencies, community-based organizations, Tribes, and other stakeholders to protect community health from extreme heat to leverage resources and opportunities. For example, Public Health, Emergency Services, and other agencies at the County level can partner with city government agencies within their jurisdiction, along with Tribes, community- and faith-based organizations, and other partners to ensure coordination and collaboration regarding planning, preparedness, and response in the face of extreme heat (and other climate-related threats).

Taking Action: Considerations and Scenarios

The information below provides additional considerations and ​guidance on actions you can take (under different scenarios) to help keep community members safe, particularly those most sensitive or vulnerable to heat.

SCENARIO: If air conditioning is not available in someone’s home:

  • Provide information on when it may be too hot to safely stay at home (including during power outages):

    • It may no longer be safe for people to stay at home when indoor air temperatures start getting into the 80s (well before 90 degrees F).[11] This is especially the case for populations at higher risk of heat-related health impacts, where it may no longer be safe at even lower indoor temperature thresholds.

    • There is also increased risk of overheating in homes when high temperatures last multiple days and/or there is little to no cooling at night. 

    • Residents on the upper floors of buildings will feel the effects of rising heat, which can elevate room temperatures and make it more difficult to maintain a consistent internal temperature if air conditioning is not available or is not used, or if ventilation is restricted.[12]

    • Even if there is access to air-conditioning at home, people with limited or fixed incomes may not choose to use it because of concerns about energy costs (see below for additional information about programs to assist with energy bills and home energy-efficiency upgrades).

    • ​When indoor air ​temperatures are really hot (high 90s), electric fans will not prevent heat-related illness since fans do not cool the air – they only move air around.[13​]

    • When indoor air temperatures get too hot to remain at home, provide guidance on transportation options to cooling centers (see below information on cooling centers and transportation).

    • Energy Assistance and Home Energy-Efficiency Upgrade Programs

      Local, State, and federal programs may be available to help residents pay their energy bills, as well as to support home energy efficiency upgrades and health and safety improvements to qualifying low-income households. To learn more, please see:​

      • California Department of Community Services and Development (CSD):

      • ​Low-Income Home Energy Assistance Program (LIHEAP)

      • Weatherization Assistance Program (WAP)

      • Low-Income Weatherization Program (LIWP)

      • California Public Utilities Commission (CPUC): 

      Local or regional utility providers (such as PG&E, SCE, or SDG&E) usually have similar programs to provide energy efficiency and weatherization services, or help pay utility bills.

  • Provide information on how to stay cool at home (if people can safely do so):

    • Use a fan to stay cool. 

      • Ceiling fans: setting fan to rotate counterclockwise will push air down. Check to see if your ceiling fan can do this.

      • REMINDER: While electric fans might provide some comfort, when temperatures are really hot, they will not prevent heat-related illness.

    • Keep blinds and drapes closed.

    • Freeze wet cloths to put on your neck, wrists, or head. Use other frozen items (e.g., bags of frozen veggies, etc.).

    • Take a cold shower or bath.

    • Close doors in unused rooms to keep cold air where you need it.

    • Turn on bathroom and stove top fans to suck hot air out.

    • Use your stove and oven less to maintain a cooler temperature in your home.

    • ​​Watch for signs of heat illness​ and seek help if needed.

SCENARIO: If someone lacks acce​ss to consistent housing or is unhoused:

​For Those Who Can ​Travel to Another Location:

  • ​Provide information on locations to stay cool:

    • Cooling centers: 

      • ​Check the CalOES Cooling Centers landing page

      • Check with other local county or city agencies on available resources. 

        • Search for Cooling and/or Community Centers (i.e., use Google Maps or other tools -- search “community / cooling centers near me”).

        • Search for Clean Air Centers / Shelters.

        • Search for city or other government buildings that can provide relief.

      • California Public Utilities Commission (CPUC) Cooling Centers webpage (including links to cooling centers in utility territories). 

      • ​CONSIDERATIONS:

        • ​Confirm availability of drinking water at cooling / respite centers, and encourage hydration

        • Ensure that pets are also allowed at the cooling centers (indoors - not just kenneled outside), while also being sensitive to the needs of those with allergies to pet dander. Consider having a separate area for pets.

        • ​CDPH Cooling Centers Guidance for Local Health Jurisdictions

          For additional guidance for local health jurisdictions to support a safe, clean environment for visitors and staff at cooling centers, please view the CDPH Cooling Centers Guidance ​​


    • Other public places with air conditioning: 

    • Public parks, fairgrounds, and other public areas with shade or other cooling measures:

      • Search for local public parks and other shaded public spaces (i.e., use Google Maps or other tools -- search “parks with shade near me”).

      • Search for public pools or water access.

      • Search for local / regional fairgrounds that have been activated as cooling centers.

      • Search for regional and/or state parks

      • Search for online mapping tools that show where shade will occur throughout the day (e.g., Shademap, Shadowmap -- please note, these specific tools have not been thoroughly vetted by CDPH, and CDPH does not necessarily endorse using these tools -- they are included here as examples).

    • Call 2-1-1 to find essential community services

      • Call to find locations and resources for staying safe during extreme heat (e.g., call to find local cooling center; for San Diego County, seniors, people with disabilities or those on limited incomes can request a free electric fan from the county at no cost by calling 211*).

        • REMINDER: While electric fans might provide some comfort, when temperatures are really hot, they won’t prevent heat-related illness.

      • 211 can provide information in different languages.

      • Call to request transportation services information (see more below).

For Those Who Cannot Easily Travel to Another Location: 

  • ​​Encourage and facilitate buddy systems or other arrangementsfor regularly checking in on heat-vulnerable individuals by family, friends, neighbors, and/or colleagues during hot weather.

  • Activate and deploy home visiting and other programs to check on people and provide relief where they are

    • This can include In-Home Supportive Services (IHSS) workers, asthma home visitors, Black Infant Health home visitors, community health workers / promotores, Meals on Wheels, nurse home visitors, CalWORKs Home Visiting Program, or any other local health and human services or programs (including Child, Family, and Adult Services).

    • Partner with local / regional community-based organizations, faith-based organizations, mutual-aid networks, Voluntary Organizations Active in Disaster (VOAD), Community Emergency Response Teams, and other community service organizations to check on priority populations and provide services and assistance.

    • Provide water, fans, portable shade and other protective measures (e.g., hats, umbrellas, fabric shade coverings, clothes that are looser / more breathable, etc.), food and medication (especially if power is out).​

  • Provide support to unhoused residents: 

    • Provide direct resources, including water, shade structures, ice, and other basic needs. 

    • Provide suggestions for unhoused people and those living in tents on strategies to stay safe and cool, for example, simple instructions on how to string up tarps or other coverings in such a way that provides shade and ventilation while reducing heat build-up.​

SCENARIO: If someone is taking medication:

For people taking psychotropic medications:

  • Provide information based on the Substance Abuse and Mental Health Services Administration’s (SAMHSA) Tips for People Who Take Medication: Coping with Hot Weather (PDF)

    • ​People taking certain psychotropic medications (antidepressants, anti-anxiety medications, stimulants, antipsychotics, and mood stabilizers) may be at greater risk of heat illness when temperatures increase. This is because some psychotropic medications interfere with a person’s ability to regulate heat and their awareness that their body temperature is rising.[14] 

For older adults taking medications:​

  • Provide information based on the CDC’s Older Adults and Extreme Heat webpage

    • Older adults may not be able to adjust to sudden temperature changes quickly because of certain medications they take or chronic illnesses that affect their ability to regulate body temperature.[15]

    • ​Commonly used medications by older adults that can increase the risk of heat-related illnesses include (but are not limited to) diuretics, beta blockers, antidepressants, antipsychotics, and anticholinergics. Along with potentially affecting thermoregulation, these medications can lead to dehydration, electrolyte imbalance, reduced sweating, decreased sensation of thirst, cognitive impairment, and other effects that increase risk of heat-related illness.[16​​​]​

SCENARIO: If someone has or cares for a pet or other animal:

  • Provide information on how to protect pets during hot weather by referring to the CDPH Protecting Your Pet During Hot Weather webpage

    • Never leave pets in a parked vehicle. Even cracked windows won’t protect your pet from suffering from heat stroke, or worse, during hot summer days.

    • Pets and companion animals feel the heat just as much as humans do and they can also suffer from heat-related illnesses. Heat stroke in pets is a life-threatening emergency and can lead to organ damage or death if not treated quickly. Know the symptoms of overheating for animals, including excessive panting or difficulty breathing, increased heart and respiratory rate, drooling, mild weakness or lethargy, stupor or even collapse, excessive thirst, and vomiting or diarrhea.

  • Help establish or provide information on pet-friendly cooling centers

    • It is important to work with your local cooling centers to allow pets and other companion animals inside (while reserving safe space for people with animal allergies), since many people may not want to or are not able to leave their pets behind.​

For those with livestock and/or other farm animals:


What Other Heat Guidance is Available?​

​Protecting Students Engaging in Sports and Strenuous Activities:

CDPH Health Guidance for Schools on Sports and Strenuous Activities During Extreme Heat
The CDPH health guidance for schools provides additional or supplemental information and guidance – it does not replace local plans. If a school or local jurisdiction has an existing heat emergency or emergency action plan, consult with the existing plan first.

Key Take-Aways for School / Athletics Administrators:

  • Know your location’s “HeatRisk” level to determine when to cancel activities or move to alternative activities in cooled indoor spaces. If a circumstance is unclear or uncertain, cancel.

  • Be aware that multiple days of extreme high temperatures will make students and athletes more vulnerable to heat illness.

  • Always monitor for exertional heat illness. Air temperature, humidity, direct sunlight, and other factors can increase risk of heat illness.

  • Be aware that exertional heat stroke is life-threatening. Exertional heat stroke can occur within the first 60 minutes of exertion and may be triggered without exposure to high ambient temperatures.

  • Proceed with extra caution in scenarios where extreme heat occurs suddenly, lasts an extended period of time, and/or reaches new high temperatures. Generally, in these scenarios, very few outdoor activity participants (or those participating in indoor spaces without cooling) are “acclimatized.”


Protecting Workers from Extreme Heat:

Cal/OSHA Heat Illness Prevention for Outdoor Workers (en Español)

  • ​California employers are required to take these fou​r steps to protect outdoor workers from heat illness

    • Training: Train all employees and supervisors about heat illness prevention. 

    • Water: Provide enough fresh cool water so that each employee can drink at least 1 quart (four 8-ounce glasses) of water per hour, and encourage them to do so.

    • Shade: Provide access to shade and encourage employees to take a cool-down rest in the shade for at least 5 minutes. They should not wait until they feel sick to cool down.

    • Planning: Develop and implement written procedures for complying with the Cal/OSHA Heat Illness Prevention Standard.

  • The Cal/OSHA Heat Illness Prevention eTool contains real world examples of heat illness; Cal/OSHA’s heat illness prevention regulation; information on employer’s Heat Illness Prevention Plan; best practices; employer sample procedures for heat illness prevention; and other resources.

  • Guidance on “acclimatization,” or the “temporary adaptation of the body to work in the heat that occurs gradually when a person is exposed to it. Acclimatization peaks in most people within four to fourteen days of regular work for at least two hours per day in the heat.” Visit the Cal/OSHA eTool’s Acclimatization page.

Farmworker taking a water break in the shade

Health Care Facilities​

CDPH All Facilities Letter (AFL 23-20) - Hot Summer Weather Advisory

  • This AFL reminds health care facilities to implement recommended precautionary measures to keep individuals safe and comfortable during extremely hot weather.

  • Facilities must have contingency plans in place to deal with the loss of air conditioning, or in the case when no air conditioning is available, take measures to ensure patients and residents are free of adverse conditions that may cause heat-related health complications.

  • Facilities must report extreme heat conditions that compromise patient health and safety and/or require an evacuation, transfer, or discharge of patients. 


Child Care Licensees and Providers

California Department of Social Services (CDSS) - Provider Information Notice (PIN): Extreme Heat Hazard Awareness Focusing On Infants and Young Children (PDF)

  • Licensees and Providers must take precautions to ensure the health and safety of children when experiencing extreme weather conditions, such as high heat. 

  • This PIN provides information about high heat hazards specific to child care providers caring for young children. 

  • Per Title 22, Section 101239 for child care centers, the licensee shall maintain the temperature in rooms that children occupy between a minimum of 68 degrees F and a maximum of 85 degrees F.


Cooling Centers Guidance for Local Health Departments

CDPH Local Health Department Cooling Centers Guidance

Cooling centers (a cool site or air-conditioned facility designed to provide relief and protection from heat) are used by many communities to protect health and mitigate heat impacts during heat events, especially for high-risk populations that are disproportionally affected by extreme heat. This document provides general guidance for Local Health Jurisdictions to support a safe, clean environment for visitors and staff at cooling centers.​

  • Cal OES Accessible Cooling Centers Guide (PDF) - Guide to support jurisdictions in planning for, and operating, accessible Cooling Centers that can serve people with disabilities and individuals with access and functional needs in an inclusive and equitable manner. 


Addressing Air Quality Impacts During Extreme Heat

  • Higher temperatures can lead to an increase in ozone, a harmful air pollutant.[17] Visit the AirNow website to check the Air Quality Index (AQI)​ in your area to determine if air quality is healthy or unhealthy, and to access resources for protecting community health from poor air quality .​​

  • Hotter temperatures and drought conditions can increase the risk of wildfires. Wildfire smoke can severely impact air quality locally and downwind. Heath effects from exposure to particulate matter in wildfire smoke can include eye and lung irritation, exacerbation of asthma, and other impacts.[18] Learn more about addressing the health effects of wildfire smoke here: CDPH Wildfire Smoke - Considerations for California’s Public Health Officials (PDF).​


Are There Examples of Local Heat Response Measures?

Local Health Jurisdiction Response Examples from the 2022 September Heat Emergency

Madera County:

  • Sending out information through multiple communication channels such as:

    • Madera County site  

    • Social media

    • Exploring other direct push messaging through OES text system and school district parent messaging (which has become a really strong messaging platform – parents in jurisdictions got used to looking at it all the time during COVID)

  • Through the Sheriff’s Program site​ 

    • “Elder Orphans is a telephonic messaging service which stores subscriber’s name, telephone number, address, emergency contact information, and call times. The program was created by the Madera County Sheriff’s Office to meet the needs of Madera County’s Senior Citizens who live alone. Elder Orphans is a free house check calling program for people who want daily contact by receiving a pre-recorded message on their home phone. You select when you want us to call you and how often.”

Trinity County:

  • ​Local protocol: Maintain open lines of communication with our utility providers to know whether they expect disruption to their systems. In this case, local utility, PG&E, is very good at communicating with their customers directly if there are any concerns. Trinity County distributes messaging via social media about staying cool and limiting outdoor activity during excessive heat. Due to the fires, Trinity County also has ‘clean air centers’ that can double as a cooling center for the public and these are also advertised to the community.

Yuba / Sutter Counties:

  • Ensure that pets are allowed at the cooling centers (indoors - not just kenneled outside) 

  • Transportation is very important so ensure that local transit is open (especially during holidays and weekends)

  • Outreach to Access and Functional Needs clients and IHSS clients is important to ensure they have all the information and assistance that they need

  • Consider having specific cooling options for unhoused clients separate from general population

San Francisco City / County:

  • Developed internal Extreme Heat public health response guidance document for the Department

  • Provides information on extreme heat emergencies, heat-related health conditions, vulnerable populations, temperature thresholds, activation and notification phases, potential city-wide impacts, lead response and partner agencies, and more.

  • Key Consideration for Vulnerable Populations: Guidance for San Francisco population (and other populations and geographic locations) that have historically not experienced extreme heat events for extended durations:

    • ​​“the population – in particular…vulnerable groups… -- has greater difficulty acclimating to long durations of extremely high temperatures. This causes an increased risk of heat stress and of heat related illness, which could subsequently result in death. Furthermore, the housing stock in San Francisco is also less likely to have central air conditioning both because of its age and because of the typically cooler climate.”

Los Angeles County

  • Ready LA County - Extreme Heat site​ published

    • ​​Comprehensive / centralized website for providing locations of cooling centers, guidance on staying safe during extreme heat, and more.​


What Other Heat Planning and Response Tools Are Available?

​Climate Change and Health Vulnerability Indicators (CCHVIs) for California

Identifying and Prioritizing Communities with Greater Climate Change and Health Vulnerability

Utilize the CDPH Climate Change and Health Vulnerability Indicators (CCHVIs) for California​ and data visualization platform (CCHVIz) to help define the scope of climate impacts and identify the populations and locations that are most vulnerable to those impacts, including for extreme heat.

The indicators are grouped into three types: 

  1. Environmental or Climate Exposure Indicators, including for heat, air quality, drought, wildfires, and sea level rise. 

  2. Indicators that speak to a community’s capacity to adapt to climate exposures, including things like air conditioning ownership, tree canopy, impervious surfaces, and public transit access. 

  3. And lastly, indicators that account for populations with greater sensitivity to climate exposures – including children and elderly, those living in poverty, and data on race and ethnicity, linguistic isolation, disability, and more. 

The data can be downloaded from the CDPH website, along with a description of why each indicator is relevant to climate change and health equity. ​​


California Heat Assessment Tool (CHAT)

Exploring and Understanding How Extreme Heat Will Impact Specific Communities Across California Using Heat Health Data

The California Heat Assessment Tool (CHAT) allows users to better understand the determinants of heat-related health impacts in your community and prioritize protecting those who are most vulnerable. You can use CHAT to explore how Heat Health Events (HHEs) are projected to change in your area at the census tract level (a Heat Health Event is any heat event that generates public health impacts, regardless of the absolute temperature). CHAT was built for planners, policymakers, public health practitioners and community members who are committed to mitigating the public health impacts of heat in their communities.


California Healthy Places Index (HPI): Extreme Heat Edition 

Understanding Underlying Heat Vulnerability and Resilience Characteristics of a Community

​The California Healthy Places Index (HPI): Extreme Heat Edition is a tool developed by the Public Health Alliance in partnership with the UCLA Luskin Center for Innovation. The tool provides datasets on projected heat exposure for California, place-based indicators measuring community conditions and sensitive populations. It also provides a list of resources and funding opportunities that can be used to address extreme heat.

The tool can be used to:

  • Understand underlying heat vulnerability and resilience characteristics of a community

  • Identify resources to mitigate adverse effects of extreme heat

  • Prioritize public and private investments, resources and programs


​​UCLA Heat Maps

Find out which communities are at greatest risk of harm during extreme heat days ​

Developed by the University of California at Los Angeles (UCLA) Center for Healthy Climate Solutions and the UCLA Center for Public Health and Disasters, the UCLA Heat Maps is an interactive mapping tool for displaying heat-related health outcomes in California, showing the excess daily emergency room visits that occur on an extreme heat day compared to the usual, non-extreme heat day. It shows this excess by county and zip code. By using the map, public health professionals, emergency service providers, urban planners, legislators, health and human services providers, non-governmental organizations, and communities themselves can find out which neighborhoods across the state are at greatest risk of harm during extreme heat events.​


Heat Safety Tool App (OSHA-NIOSH)

Planning Outdoor Work Activities Based on How Hot It Feels

The OSHA-NIOSH Heat Safety Tool​ is a useful resource for planning outdoor work activities based on how hot it feels throughout the day. It has a real-time heat index and hourly forecasts specific to your location. It also provides occupational safety and health recommendations from the Occupational Safety and Health Administration (OSHA) and the National Institute for Occupational Safety and Health (NIOSH)​.

The OSHA-NIOSH Heat Safety Tool features:

  • A visual indicator of the current heat index and associated risk levels specific to your current geographical location

  • Precautionary recommendations specific to heat index-associated risk levels

  • An interactive, hourly forecast of heat index values, risk levels, and recommendations for planning outdoor work activities

  • Location, temperature, and humidity controls, which you can edit to calculate for different conditions

  • Signs and symptoms and first aid for heat-related illnesses

Download on the Apple App Store

Download via Google Play ​

Key considerations for using the app (from CDC Heat Safety Tool webpage):

  • Heat index (HI) values were created for shady, light wind conditions, so exposure to full sunshine can increase heat index values by up to 15°F.

  • The simplicity of the HI makes it a good option for many outdoor work environments (if no additional radiant heat sources are present, such as, fires or hot machinery). However, if you have the ability, NIOSH recommends using wet bulb globe temperature (WBGT)-based Recommended Exposure Limits (RELs) and Recommended Alert Limits (RALs) in hot environments.

  • Use of the HI or WBGT is important, but other factors such as strenuous physical activity also cause heat stress among workers. Employers should have a robust heat stress prevention program that ensures workers are protected.

  • NIOSH and OSHA are considering new scientific data related to the HI levels, and considering how to best incorporate the evolving science. It is important to regularly download updates to ensure you are using the latest version of the app.


​​Flex Alerts

Working Together to Prevent Power Outages During Extreme Heat

Issued by the California ISO, Flex Alerts are voluntary calls for consumers to conserve electricity in order to minimize discomfort, help with grid stability, and ensure the power stays for helping communities stay cool. The power grid is usually most stressed from higher demand and less solar energy between 4 p.m. and 9 p.m. During this time, consumers are urged to conserve power by:

  • Setting thermostats to 78 degrees or higher, if health permits.

  • Avoiding use of major appliances and turning off unnecessary lights. 

  • Avoid charging electric vehicles while the Flex Alert is in effect.

Consumers are also encouraged to pre-cool their homes and use major appliances and charge electric vehicles and electronic devices before 4 p.m., when conservation begins to become most critical. 

Consumers can sign up for Flex Alerts and participate in conserving energy when Flex Alerts are issued. A Flex Alert is typically issued in the summer when extremely hot weather drives up electricity use, making the available power supply scarce. Reducing energy use during a Flex Alert can help stabilize the power grid during tight supply conditions and prevent further emergency measures, including rotating power outages.

Sign up to receive Flex Alerts here

Learn more about Flex Alert here

National Integrated Heat Health Information System (NIHHIS) - Heat.gov

National Heat and Health Information to Reduce the Health, Economic, and Infrastructural Impacts of Extreme Heat

Heat.gov​ is the web portal for NIHHIS, and is a collaboration of NIHHIS Federal partners, which include the National Oceanic and Atmospheric Administration, Centers for Disease Control and Prevention, Assistant Secretary for Preparedness and Response, Environmental Protection Agency, Department of Housing and Urban Development, Federal Emergency Management Agency, National Institute for Occupational Safety and Health, Department of Veterans Affairs, Forest Service, National Park Service, Department of Health and Human Services, National Institute of Environmental Health Sciences, Occupational Safety and Health Administration, and Substance Abuse and Mental Health Services Administration. Access Heat.gov’s Extreme Heat Planning and Preparation resources here​.

What Funding Opportunities Are Available to Increase Community Resilience to Extreme Heat?​

​​There are state grant programs available to support climate resilience efforts, including for extreme heat and community resilience planning and implementation (pending available funding -- please check the funding status for each grant program below):

Search for additional funding opportunities through the California Grants Portal​

References

[1] National Weather Service (NWS). Weather Related Fatality and Injury Statistics

[2] Center for Disease Control and Prevention (CDC). Keep Your Cool in Hot Weather!​

[3] Tracking California. Heat Related Deaths Summary Tables.

[4] Protecting Californians From Extreme Heat: A State Action Plan to Build Community Resilience. 2022. California Natural Resources Agency (PDF). 

[5] Liu J, et al. 2021. Is there an association between hot weather and poor mental health outcomes? A systematic review and meta-analysis. Environment International. Vol. 153.

[6] Sun K, et al. 2021. Passive cooling designs to improve heat resilience of homes in underserved and vulnerable communities. ​Energy and Buildings. Vol. 252. 

[7] NWS. HeatRisk - Understanding HeatRisk. 

[8] Note that common illnesses can also be exacerbated by extreme heat including autoimmune conditions; asthma, COPD, and allergies; migraines; heart disease; and autoimmune diseases including multiple sclerosis (MS), lupus, and rheumatoid arthritis (RA).

[9] Vigorous activity is defined by the Centers for Disease Control as activities greater than 6.0 METs. Specific examples can be found on the CDC’s resource here (PDF).

[10] Substance Abuse and Mental Health Services Administration (SAMHSA). Heat Health Awareness: Why it’s Important for Persons with Substance Use Disorders and Mental Health Conditions, Caregivers and Health Care Providers.

[11] Estimation of maximum safe indoor air temperatures is based on the World Health Organization’s (WHO) research and guidelines and the policies of other southwestern United States jurisdictions for establishing maximum safe indoor air temperatures. For more information, see the World Health Organization’s (WHO) Housing and Health Guidelines; also see code language for maximum temperature thresholds set by local U.S. jurisdictions, including Palm Springs, CA; Phoenix, AZ; Tempe, AZ; Tucson, AZ; Clark County, NV; and El Paso, Texas. 

[12] US Environmental Protection Agency (EPA). 2016. Excessive Heat Events Guidebook. 

[13] CDC. Frequently Asked Questions (FAQ) About Extreme Heat: “How effective are electric fans in preventing heat-related illness?” 

[14] SAMHSA. Tips for People Who Take Medication: Coping with Hot Weather (PDF). 

[15] CDC. Older Adults and Extreme Heat. 

[16] M Alied and N T Huy. 2022. A reminder to keep an eye on older people during heatwaves. The Lancet. 3:10, E647-E6​48. 

[17] CDC. Protect Yourself From the Dangers of Extreme Heat.

[18] California Office of Environmental Health Hazard Assessment (OEHHA). Wildfires. ​​

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