Extreme heat kills more Americans every year than any other weather-related hazard — including floods, hurricanes, and tornadoes combined. The CDC and NOAA estimate extreme heat events claim an average of more than 1,300 American lives annually — a number widely considered to be significantly undercounted. Ready.gov’s Extreme Heat Hazard Information Sheet identifies heat as one of the nation’s most underestimated hazards, and the situation is expected to worsen as climate patterns shift.
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Why Extreme Heat Is So Dangerous
Heat is dangerous precisely because it is insidious. Unlike a hurricane or tornado, a heat wave often arrives without dramatic visual cues. The human body regulates its temperature through perspiration, but when heat and humidity are both high, sweating becomes less effective. When the body can no longer cool itself, the result can be heat cramps, heat exhaustion, or the life-threatening condition known as heat stroke. Some populations are far more severely affected: adults 65 and older, children under 4, people with chronic medical conditions, people taking certain medications, people without air conditioning, outdoor workers and athletes, and people experiencing poverty or housing insecurity.
Heat-Related Illness: Signs and Response
Heat Cramps
Muscle spasms from heavy sweating during strenuous activity. Move to a cool location, drink water or a sports drink, and rest. Seek medical attention if cramps last more than 1 hour.
Heat Exhaustion
Symptoms: heavy sweating, weakness, cold or pale and clammy skin, weak pulse, nausea or vomiting, possible fainting. Move to a cool location, loosen clothing, apply cool wet cloths, and fan the person. If vomiting occurs or symptoms worsen, seek emergency medical care.
Heat Stroke
A medical emergency. Body temperature above 103°F, hot and dry skin, rapid and strong pulse, possible unconsciousness. Call 911 immediately. Cool the person rapidly with whatever is available. This is life-threatening — do not delay emergency care.
Before Extreme Heat Arrives: Preparation Steps
- Know your local heat resources. Find out where the nearest cooling center is. Most cities and counties open cooling centers at libraries, community centers, and shopping malls during heat emergencies.
- Check on vulnerable neighbors. Identify elderly, disabled, or isolated neighbors who may not have air conditioning. Check on them daily during heat waves.
- Maintain your air conditioning. Service your AC before summer. If you do not have AC, identify a cool location to spend the hottest hours (typically 11am–6pm).
- Install window coverings. Reflective window film, solar shades, or external awnings significantly reduce indoor heat buildup.
- Prepare your body. If you work outdoors or exercise in summer, acclimatize gradually over 10–14 days to allow your body to adapt to heat.
During an Extreme Heat Event
- Stay cool indoors — air conditioning is the most effective way to prevent heat illness
- Drink plenty of water and electrolyte drinks; avoid alcohol and caffeine
- Wear lightweight, loose-fitting, light-colored clothing
- Avoid strenuous activity during the hottest parts of the day
- Never leave children or pets in parked cars — temperatures can reach 120°F within minutes
- Take cool showers or baths if overheated
- Monitor local weather reports and emergency alerts; follow official guidance about cooling centers
How PubSafe Supports Community Resilience During Heat Emergencies
Heat emergencies are unique in that their victims often cannot advocate for themselves. A community connected through PubSafe can close this gap by organizing welfare check networks for vulnerable community members during heat waves, sharing cooling center locations within the community network, allowing members to signal safety status or request assistance, and integrating heat emergency alerts from local authorities to reach community members who may not be monitoring mainstream media.
In the aftermath of the 1995 Chicago heat wave — which killed more than 700 people in one week — investigators found that social isolation was a key contributing factor. Connected communities are safer communities. PubSafe is the tool for building that connection before the next heat emergency arrives.
Resources
- Ready.gov Extreme Heat page
- CDC Extreme Heat: cdc.gov/niosh/topics/heat
- NOAA Heat Safety Tips: weather.gov/safety/heat
Download the Ready.gov Extreme Heat Hazard Information Sheet, save the number for your local cooling center, and connect your neighborhood on PubSafe.
The Science of Urban Heat Islands and Extreme Heat
Urban areas experience significantly higher temperatures than surrounding rural areas — a phenomenon known as the urban heat island (UHI) effect. The UHI is caused by the replacement of natural vegetation with heat-absorbing materials like asphalt and concrete, the heat generated by vehicles and buildings, and the reduced evapotranspiration that occurs when vegetation is removed. Studies have found that urban temperatures can be 2–7°F higher than surrounding rural areas, and on calm clear nights, the difference can exceed 22°F in some cities.
For city residents, the UHI means that heat emergencies are more severe than regional forecasts may suggest. A temperature of 95°F in a suburban area may correspond to 100–102°F in an urban core. Cities are responding to the UHI with a range of interventions: urban tree canopy programs (trees provide shade and evaporative cooling), green roofs and cool roofs (which reflect more sunlight than traditional roofing materials), cool pavement technologies, and urban park expansion. These investments have measurable public health benefits — a study in Phoenix found that urban trees reduced heat-related emergency department visits in surrounding neighborhoods.
Understanding the UHI is important context for individual preparedness. If you live in an urban area, assume heat forecasts underestimate your actual exposure. Monitor indoor temperatures, not just outdoor forecasts. Install a thermometer in your home and use it to determine when conditions inside your residence have become dangerous.
Heat Safety for Specific Vulnerable Populations
While extreme heat poses risks to everyone, certain populations face disproportionate danger and require targeted protection strategies.
Athletes and outdoor workers face sustained heat exposure during the highest-risk periods of the day. OSHA mandates that employers provide water, rest, and shade for outdoor workers and acclimatize new workers to heat gradually. The National Athletic Trainers’ Association (NATA) provides evidence-based protocols for managing heat illness in athletic settings, including the use of cold water immersion — the most effective treatment for severe heat stroke — at athletic events.
People with mental illness are at significantly elevated risk for heat-related death, both because some psychotropic medications impair the body’s heat regulation and sweating response, and because mental illness can affect the behavioral responses needed to protect oneself from heat. Mental health providers should discuss heat safety plans with vulnerable patients before summer and ensure they have access to cooling resources.
People experiencing homelessness are among the most at-risk populations during heat emergencies, with limited access to shelter, cooling, and healthcare. Many cities open overnight emergency cooling shelters specifically for unhoused individuals during heat emergencies, and community organizations provide water distribution, wellness checks, and transportation to cooling resources. If you encounter someone who appears to be experiencing heat stroke — hot, dry skin; confusion; loss of consciousness — call 911 immediately and begin cooling measures.
National and International Responses to Extreme Heat
In response to growing recognition of heat as a deadly public health crisis, cities and countries around the world are developing formal heat action plans — coordinated, government-led responses that activate specific services and communications when heat thresholds are exceeded. Philadelphia, Phoenix, Miami, and Los Angeles are among the U.S. cities that have implemented formal heat action plans. Spain, France, and India have developed national-level heat action plans following devastating heat events that killed thousands.
Some cities have appointed Chief Heat Officers — officials specifically tasked with coordinating the city’s heat preparedness and response. Miami’s Chief Heat Officer has implemented programs ranging from early-morning cooling hours at libraries to expanded urban tree plantings in high-risk neighborhoods. These institutional responses complement individual preparedness — and your engagement with community platforms like PubSafe helps ensure that official resources reach every community member who needs them during the next heat emergency.
