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Extreme heat events are one of the most common causes of weather-related deaths in the United States – and the number of heat-related deaths is rising.

Botanical Gardens, Sydney, New South Wales, Australia.

Botanical Gardens, Sydney, New South Wales, Australia.

More frequent and severe heat waves are likely to occur as climate change continues to change weather patterns. These events pose a serious public health risk.

As we head into summer, there are steps you can take to prevent illness, injury, and death related to hot weather. Heat waves occur when temperatures reach unusually high levels compared to some historic averages for a specific area and remain high for a prolonged period. Humid or muggy conditions can add to the discomfort and severity of a heat wave. It is during these extended periods that extreme heat can be dangerous. People suffer heat-related illness when the body’s temperature control system is compromised. Your body normally cools itself by sweating. But under some conditions, sweating just isn’t enough and your body temperature rises rapidly. When the humidity is high, sweat will not dry as quickly. This prevents your body from releasing heat quickly. Very high body temperatures might damage your brain or other vital organs.

Certain groups are at a higher risk for heat-related illness or injury. These groups include:

  • adults over 65 years old and children under four years old,
  • those with existing medical problems such as heart disease,
  • people with no access to air conditioning

Tips to Prevent Heat-related Illnesses

Stay cool. Keep your body temperature cool to avoid heat-related illness.

  • Stay in air-conditioned buildings as much as possible.
  • Find an air-conditioned shelter.
  • Do not rely on a fan as your primary cooling device.
  • Avoid direct sunlight.
  • Wear lightweight, light-colored clothing.
  • Take cool showers or baths.
  • Check on those most at-risk twice a day.

Stay hydrated. Because your body loses fluids through sweat, you can become dehydrated during times of extreme heat.

  • Drink more water than usual.
  • Don’t wait until you’re thirsty to drink more fluids.
  • Avoid alcohol or liquids containing high amounts of sugar.
  • Remind others to drink enough water.

Stay informed. Stay updated on local weather forecasts so you can plan activities safely when it’s hot outside.

  • Check local news for extreme heat alerts and safety tips.
  • Learn the symptoms of heat illness.

A tool from the Centers for Disease Control and Prevention (CDC) is helping us understand the connection between climate change, extreme heat and public health. The National Environmental Public Health Tracking Network (EPHT) is the best Internet resource that explains the relationships between some environmental and health problems. It does this by collecting information that would traditionally be kept separately by many government and public health agencies. For example, the data available for climate change and health are from 5 different sources. Bringing it all together can help us discover the connections between our health and the environment.

Key Facts

About Climate Change and Extreme Heat

  • Climate change refers to any major change in climate and weather patterns which lasts for ten years or more. Examples include temperature, precipitation, or wind.
  • As a result of the changing climate, serious weather events such as heat waves, droughts, flooding, tropical cyclones, and rises in sea level happen more often.
  • Heat waves occur when temperatures reach unusually high levels compared to some historic averages for a specific area and remain high for a prolonged period.

The Connection between Climate Change, Extreme Heat and Health

  • Adverse health effects from extreme heat events are the most common cause of weather related deaths in the United States. On average, they cause more deaths each year than hurricanes, lightning, tornadoes, floods, and earthquakes combined.
  • Heat also increases ground-level ozone concentrations, causing direct lung injury and increasing the severity of respiratory diseases such as asthma and chronic obstructive pulmonary disease.
  • The following groups of people have a higher risk of experiencing negative health effects related to climate change.
    • People who are elderly, very young, disabled, poor, or live alone,
    • People with existing medical conditions such as heart disease or asthma, and
    • People who live in urban areas with high air pollution or in old buildings with poor cooling systems, or have no air conditioning.

To learn more about CDC’s Climate Change and Extreme Heat on the Environmental Public Health Tracking Network please visit:

CDC’s Environmental Public Health Tracking Network

CDC’s Climate and Health Program

Written By:


EPHT Program Manager and Epidemiologist in the Bureau of Environmental Health

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