Heat waves can be lethal. In 2023, one of the hottest years on record, researchers linked sweltering weather to more than 2,300 U.S. deaths. That same year, nearly 120,000 Americans were admitted to emergency departments for heat-related illnesses.
“What makes extreme heat most dangerous for people is that it is an invisible threat,” says Kevin Kelley, the senior director for community preparedness programs for the American Red Cross. “With extreme heat you might not immediately recognize some of the risks as you navigate your day.”
Why Extreme Heat Poses Health Risks
Exposure to high heat threatens health because the body can’t cool itself down fast enough. This can lead to myriad issues.
“We can become confused due to the heat and may not react appropriately to the body telling us we are too hot, further exacerbating acute heat exposure,” says Daniel Smith, PhD, professor and researcher at Emory University’s School of Nursing in Atlanta.
Dehydration can put severe stress on the heart, leading to cardiovascular problems.
“When happening repeatedly, dehydration and heat stress can also cause kidney failure in the long term,” Dr. Smith says.
Some People Are More Vulnerable to Extreme Heat
“Extreme heat can be dangerous for anyone, but some people are at higher risk of getting sick because their bodies have a harder time staying cool,” says Kelley.
Those most vulnerable to heat-related illness include:
Older adults, since they may not feel thirst as readily, according to Smith.
Children, whose bodies heat up faster than adults.
Pregnant people, since they have increased cardiovascular demands.
Individuals with chronic illnesses or disabilities.
People who spend more time outdoors, including athletes and workers with jobs outside.
Heat can also complicate how the body responds to certain drugs. People who take the following types of medicines should be extra cautious during high heat:
Antihistamines and decongestants can decrease sweating, which could make it harder for the body to cool off.
Beta-blockers can reduce blood flow to the skin, interfering with self-cooling.
Diuretics decrease the total amount of fluid in your body.
Psychiatric drugs, including antidepressants, stimulants, and mood stabilizers, can change how your body responds to stress, including heat.
GLP-1 weight loss and diabetes drugs can reduce hunger signals and, by extension, thirst signals.
How to Prepare for Extended Heat
Kevin Lanza, PhD, assistant professor of environmental and occupational health sciences at UTHealth Houston, urges people to have a plan ready well before the hot weather comes on full blast:
Stay informed about weather conditions. Pay attention to weather forecasts, heat indexes (how hot it feels due to temperature and humidity), and heat advisories put out by the National Weather Service.
Dr. Lanza also suggests enabling weather alerts on your phone. The free Red Cross Emergency app provides real-time weather alerts in English and Spanish along with tips for staying safe. The Occupational Health and Safety Administration offers a heat safety tool app that warns if conditions are becoming hazardous.
Make sure you have plenty of water. “I think folks are chronically dehydrated — not getting enough water to begin with,” says Lanza. While other liquids besides water can help, he warns against any beverages containing caffeine or alcohol, which can make dehydration worse.
Check your AC. Air conditioning is one of the best ways to stay safe in high temperatures, according to Lanza. Make sure your air conditioning and/or fans are working properly.
Verify that you have supplies to keep medication cool and equipment charged. Extended periods of extreme heat can sometimes lead to power outages.
Identify cool public spaces in case of heat emergency. Schools, libraries, malls, and recreation centers often provide cooling areas during extreme heat conditions.
Create a network of helpers. Family, friends, and neighbors may all be able to help in a heat emergency. Have their contact information readily available, especially if you are at greater risk of heat-related injury. “People who are socially connected have a higher likelihood of being protected during extreme weather,” says Lanza.
How to Stay Safe Once It’s Hot
The American Red Cross emphasizes these steps to take when sweltering weather arrives:
Stay hydrated. Drink a cup of water every hour, even if you don’t feel thirsty. Avoid sugary, caffeinated, and alcoholic drinks.
Seek out air conditioning. Spend time in air-conditioned places. If your home is too hot, go to a cooling center. Cool showers or baths can help too.
Dress right. Wear lightweight, loose-fitting clothes in lighter colors.
Time your outside activities. Arrange your schedule to be outdoors when the weather is less hot. If you must be outdoors for your job, take extra breaks. “According to some estimates, 30 minutes of break may be needed every hour during the hottest time of the day depending on how intense the work is,” says Smith.
Stay connected. Ask for help if you need it and check on others. Don’t forget to make sure pets have access to fresh water and shade.
What Are the Signs of Heat Exhaustion and Heat Stroke?
Smith views the two conditions as part of a continuum, with heat exhaustion as a milder condition that often comes on before the more serious heat stroke.
“The ultimate consequence of heat stroke is death,” says Smith. “It is important to note that many people think you can only have a heat stroke if you stop sweating, which is just not true. This may be seen in some people, but you can have heat stroke and still be actively sweating.”
If you experience heat exhaustion (or observe it in someone else), you should:
Stop what you’re doing.
Rest in a cool place and slowly sip water. Don’t drink if you feel sick.
Loosen your clothes and place a cool, wet cloth on your body.
Get medical help if you don’t feel better, vomit, or have heart problems.
For heat stroke, follow these directives:
Call 911.
Move to a cool place.
Remove extra clothing.
Use a wet cloth or get in a cool bath to cool down.
Don’t drink anything. A person with heat stroke may be unable to safely swallow.
Extreme Heat Is a Growing Threat
Heat-related illnesses are becoming a greater issue as climate change makes extreme weather more frequent and more likely to affect a greater swath of the world.
“Extreme heat is happening in places that traditionally don’t experience these types of temperatures,” such as the Pacific Northwest and even Alaska, says Kelley.
States that are normally hot are only getting warmer. States in the South and Southwest consistently rank the hottest, with Florida claiming the No. 1 spot for the most heat-related illnesses due to a large number of outdoor workers and older, more vulnerable individuals. It’s not unusual to see temperatures in these regions push beyond the 100 degree F mark.
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Resources
Howard J et al. Trends of Heat-Related Deaths in the US, 1999-2023. JAMA. August 26, 2024.
Allison Buttarazzi, MD, is board-certified in internal medicine and lifestyle medicine, and is a certified health and well-being coach. In her primary care practice, Dr. Buttarazzi focuses on lifestyle medicine to help her patients improve their health and longevity, and her passion is helping patients prevent and reverse chronic diseases (like heart disease, high blood pressure, and diabetes) by improving their lifestyle habits.
She is a graduate of Tufts University School of Medicine and completed a residency at Maine Medical Center. Diagnosed with celiac disease during medical school, she realized the power of improving one's health through diet and lifestyle habits, which she later incorporated into her practice.
Don Rauf has been a freelance health writer for over 12 years and his writing has been featured in HealthDay, CBS News, WebMD, U.S. News & World Report, Mental Floss, United Press International (UPI), Health, and MedicineNet. He was previously a reporter for DailyRx.com where he covered stories related to cardiology, diabetes, lung cancer, prostate cancer, erectile dysfunction, menopause, and allergies. He has interviewed doctors and pharmaceutical representatives in the U.S. and abroad.
He is a prolific writer and has written more than 50 books, including Lost America: Vanished Civilizations, Abandoned Towns, and Roadside Attractions. Rauf lives in Seattle, Washington.
