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Extreme Heat Events: What Are They and How to Stay Healthy During One

By Melissa Kluczynski, MS

Every summer more than 65,000 people in the U.S. visit the emergency room due to acute heat-related illness. Extreme heat was the leading cause of weather-related deaths in the U.S. from 2000 to 2009; and between 1999 to 2009 extreme heat exposure caused or contributed to 7,800 deaths in the U.S. Due to climate change, extreme heat events are expected to increase in the U.S. meaning that the number of heat-related illnesses and deaths will likely increase too. However, heat-related illnesses and deaths are preventable. Read on to find out more about extreme heat events and how to stay healthy during one.

What is an Extreme Heat Event? Extreme heat is when the temperature and/or humidity is much higher than normal. Extreme heat varies based on different factors including geographic location, weather conditions (e.g., cloud cover), and time of year. “Urban heat islands” refer to cities that experience longer and more severe periods of extreme heat compared to rural and suburban areas. Cities tend to be 10° warmer than rural and suburban areas because concrete and asphalt absorbs and holds heat, tall buildings reduce the flow of cool air, and lack of trees and vegetation that provide shade.

What are the Health Consequences of Extreme Heat? The most common health effects caused by extreme heat are: heat cramps (muscle pains or spasms that happen during heavy exercise), heat exhaustion (occurs after several days of exposure to high temperatures and not enough fluids), and heat stroke (life-threatening illness that occurs when body temperature rises above 106° F). Heat exhaustion and heat stroke are serious conditions that require emergency treatment. Learn more about the signs and symptoms of heat-related illness here.

Who is at Risk for Heat-Related Illness? Anyone can develop heat-related illness, including young and healthy people who participate in strenuous activities in hot weather. However, some populations are more vulnerable to heat-related illness including young children, adults aged 65 years and older, persons with disabilities, people with mental illness or chronic disease, those living in poverty or social isolation, the homeless, people who work outside, and athletes that train or compete outdoors. People with chronic health conditions (e.g., heart disease, poor blood circulation, obesity) are more vulnerable to heat-related illness because they may be less likely to sense and respond to changes in temperature and certain medications can make the effect of extreme heat worse.

How Can Heat-Related Illnesses be Prevented? The Centers for Disease and Prevention recommend the following tips for preventing heat-related illness:

  • Stay Cool:

    • Spend time in an air-conditioned place (e.g., mall, library, cooling centers)

    • Minimize direct sun exposure (limit activity to the morning and evening when it is the coolest)

    • Avoid exercising outdoors in the heat

    • Wear sunscreen

    • Do not leave children or pets in cars

    • Use electric fans

    • Take a cool shower or bath

    • Wear loose-fitting, light-colored clothes

  • Stay Hydrated:

    • Drink plenty of fluids throughout the day (avoid very sugary and alcoholic drinks)

    • Replace salts or minerals with a sports drink or fruit juice

    • Don’t forget your pets! Keep them hydrated too

  • Stay Informed:

    • Check for local updates regarding extreme heat and the location of cooling centers

    • Be aware of the signs and symptoms of heat-related illness (view the full list here)

    • Monitor friends, family, and co-workers at high-risk (check in with adults at least twice a day and more often for infants and young children)



Centers for Disease Control and Prevention. Extreme Heat. June 30, 2021. Accessed May 17, 2022.

Centers for Disease Control and Prevention. Climate Change and Extreme Heat Events. Accessed May 16, 2022.

Centers for Disease Control and Prevention. Extreme Heat Can Impact Our Health in Many Ways Infographic. Accessed May 16, 2022.

U.S. Environmental Protection Agency. Climate Change and Extreme Heat: What You Can Do To Prepare. October 2016. Accessed May 16, 2022.


Melissa Kluczynski holds a Master of Science degree in Epidemiology from the University at Buffalo and she is currently working as a Research Associate in the Department of Cancer Prevention and Control at Roswell Park Comprehensive Cancer Center in Buffalo, NY. Her research interests include chronic disease prevention and women's health.

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