Excessive heat, a 'silent killer'

Heat exhaustion or heatstroke? Know the signs of heat illness.

UPDATED: July 19, 2023. Updated to include the most recent heat statistics from the Centers for Disease Control and Prevention.

June 18, 2014

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If you plan on being out and about in summer, chances are you’ll be exposed to a lot of sun and higher temperatures.

Silhouette of an tired sportsman at sunset — Silhouette of a person at sunset during a heatwave. (Image credit: iStock)

How much heat can a person safely endure? It depends.

From 2018-2020, over 3,000 people died from heat-related causes, according to statistics from the Centers for Disease Control and Prevention.

Certain groups of people should be especially careful during hot weather conditions. For example, city-dwellers and those living in the upper floors of tall buildings or in heat-prone regions are most at-risk for heat-related illness. People who have difficulty getting around or who have health conditions are particularly susceptible. The elderly and the very young also merit special attention during periods of high heat and humidity.

NOAA's National Weather Service (NWS) and the Occupational Safety and Health Administration have partnered to increase awareness for outdoor workers and their employers during excessive heat events. As part of this effort, NWS will incorporate specific outdoor worker safety precautions when heat advisories and warnings are issued.

No matter what your job is or how you spend your free time, prevention of heat-related illness is key. Here's what you can do:

1. Be informed and stay alert

Pay close attention to heat advisories or warnings that have been issued for your community.

NOAA’s National Weather Service continually updates heat-related advisories and warnings online at weather.gov. (Click on “Excessive Heat Warning” and “Heat Advisory” under the U.S. map — if there are no current warnings or advisories in the United States, nothing will appear).

NOAA issues excessive heat warnings when weather conditions pose an imminent threat to life and heat advisories when weather conditions are expected to cause significant discomfort or inconvenience or — if caution is not taken — become life threatening.
If you do not have Internet access, you can get heat advisory and warning information by watching your local television or radio newscast or by purchasing a NOAA weather radio and tuning into NOAA Weather Radio All-Hazards.
Use the temperature and humidity to figure out the heat index for your area, a measure that tells us how hot it feels.

2. Plan for periods of extreme heat

Visit your physician for a check-up to find out if you have a health condition that may be exacerbated by hot weather.
Service your air conditioner before hot weather arrives, and obtain window fans to help cool your home.
Know where to go when weather heats up. Find cool indoor places to spend time on hot summer days, such as a local library, shopping mall, museum or aquarium.

Girl in shade at the beach. — (MorgueFile.com)

3. Know what to do and what not to do during hot weather

DO - Slow down, and reduce strenuous activity. Mow the lawn or garden in the early morning or late evening instead of midday.
DO - Dress in lightweight, nonrestrictive, light-colored clothing.
DO - Drink plenty of water or other nonalcoholic fluids.
DO - Eat light, easy-to-digest foods.
DO - Seek out shade if you have to be outdoors for extended periods. Spend more time in air-conditioned places.
DO - Check on elderly neighbors, friends and relatives to make sure they are okay.
DO - When outside, take frequent dips in the ocean or pool, or mist yourself with a water bottle. When inside, take frequent cool baths or showers and use cold compresses to cool off.
DO - Apply high-SPF sunscreen frequently when outdoors.
DO - Seek immediate medical attention if you experience symptoms of heat illness. (See chart below for symptoms, likely conditions and treatment.)

(Image credit: MorgueFile.com) — (MorgueFile.com)
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However, please remember:

DO NOT leave children, the elderly, or pets in the car for any reason, for any length of time. Look before you lock! A dark dashboard or seat can easily reach temperatures in the range of 180 to more than 200 degrees F!
DO NOT stay in the sun for long periods.
DO NOT take salt tablets unless directed by a physician.
AVOID alcoholic beverages; they can dehydrate you and increase your risk of heat stroke and other potentially fatal heat-related illnesses.

4. Know the warning signs of heat-related illness*

Tpo much exposure to heat can raise your body temperature to unhealthy levels and may make you ill — it can also be deadly. Take the precautions listed above and be on the lookout for these warning signs that you may be in trouble:

Symptom	Likely Condition	Treatment
Painful muscle cramps and spasms, usually in muscles of legs and abdomen. Heavy sweating.	Heat cramps	Apply firm pressure on cramping muscles or gently massage to relieve spasm. Give sips of water; if nausea occurs, discontinue water intake. Consult with a clinician or physician if individual has fluid restrictions (e.g., dialysis patients).
Heavy sweating, weakness, cool skin, pale and clammy. Weak pulse. Normal temperature possible. Possible muscle cramps, dizziness, fainting, nausea and vomiting.	Heat exhaustion	Move individual out of sun, lay him or her down, and loosen clothing. Apply cool, wet cloths. Fan or move individual to air conditioned room. Give sips of water; if nausea occurs, discontinue water intake. If vomiting continues, seek immediate medical attention. Consult with a clinician or physician if individual has fluid restrictions (e.g., dialysis patients).
Altered mental state. Possible throbbing headache, confusion, nausea and dizziness. High body temperature (106°F or higher). Rapid and strong pulse. Possible unconsciousness. Skin may be hot and dry, or patient may be sweating. Sweating likely especially if patient was previously involved in vigorous activity.	Heat stroke	Heat stroke is a severe medical emergency. Summon emergency medical assistance or get the individual to a hospital immediately. Delay can be fatal. Move individual to a cooler, preferably air-conditioned, environment. Reduce body temperature with a water mister and fan or sponging. Use air conditioners. Use fans if heat index temperatures are below the high 90s. Use extreme caution. Remove clothing. If temperature rises again, repeat process. Do not give fluids.

Symptom

Likely Condition

Treatment

Painful muscle cramps and spasms, usually in muscles of legs and abdomen. Heavy sweating.

Heat cramps

Apply firm pressure on cramping muscles or gently massage to relieve spasm.

Give sips of water; if nausea occurs, discontinue water intake.

Consult with a clinician or physician if individual has fluid restrictions (e.g., dialysis patients).

Heavy sweating, weakness, cool skin, pale and clammy. Weak pulse. Normal temperature possible. Possible muscle cramps, dizziness, fainting, nausea and vomiting.

Heat exhaustion

Move individual out of sun, lay him or her down, and loosen clothing.

Apply cool, wet cloths.

Fan or move individual to air conditioned room.

Give sips of water; if nausea occurs, discontinue water intake.

If vomiting continues, seek immediate medical attention. Consult with a clinician or physician if individual has fluid restrictions (e.g., dialysis patients).

Altered mental state. Possible throbbing headache, confusion, nausea and dizziness. High body temperature (106°F or higher). Rapid and strong pulse. Possible unconsciousness. Skin may be hot and dry, or patient may be sweating. Sweating likely especially if patient was previously involved in vigorous activity.

Heat stroke

Heat stroke is a severe medical emergency.

Summon emergency medical assistance or get the individual to a hospital immediately.

Delay can be fatal.

Move individual to a cooler, preferably air-conditioned, environment.

Reduce body temperature with a water mister and fan or sponging.

Use air conditioners. Use fans if heat index temperatures are below the high 90s. Use extreme caution.

Remove clothing. If temperature rises again, repeat process. Do not give fluids.

Source: Excessive Heat Events Guide Book, Environmental Protection Agency

*Please note: This information is not a substitute for expert medical care. If you should experience any of the above symptoms, seek medical assistance/advice immediately. Call 911.

See these resources on heat-related illnesses

The CDC’s Extreme Heat webpage;
OSHA’s heat illness webpage, Water. Rest. Shade; and
NOAA National Weather Service's Heat Safety Tips