Skip to main content
U.S. flag

An official website of the United States government

Heat-related Illness (Hyperthermia)

A man shields his head from the sun as he walks across the Brooklyn Bridge on a hot summer day in New York City.

The human body is great at cooling itself through natural mechanisms. Humans actually do it better than any other mammal on Earth. But extreme heat can overwhelm the body, resulting in heat-related illness.

Heat-related illness can include:

  • Heat cramps

  • Heat exhaustion

  • Heat stroke

Older adults, young children and people with chronic medical conditions are at high-risk for heat-related illness. Hundreds of people in the U.S. die every year of heat-related illness.

When you visit your National Forests and Grasslands, take the extra time to protect yourself and others from heat related illness.

  • Drink plenty of water. Avoid sugary drinks and alcohol, as they can lead to dehydration.

  • Stay in the shade whenever possible

  • Schedule the most rigorous activities for early or later in the day

  • Wear lightweight, loose-fitting, light-colored clothing

  • Keep a close eye on older adults, children, and those with chronic medical conditions

Heat exhaustion:

  • Heavy sweating

  • Weakness

  • Cold, pale, clammy skin

  • Fast, weak pulse

  • Nausea or vomiting

  • Fainting

What to do: 

  • Move to a cooler location

  • Lie down and loosen clothing

  • Apply cool, wet cloths to as much of the body as possible

  • Sip water

  • If vomiting occurs and continues, seek medical attention immediately

Heat stroke is a medical emergency. If you suspect heat stroke or see the signs below, call 911 immediately.

Heat stroke:

  • High body temperature (above 103°F)

  • Red, hot, dry, or moist skin

  • Rapid, strong pulse

  • Unconsciousness

What to do:

  • Call 911 immediately

  • Move to a cooler environment

  • Reduce body temperature with cool cloths or with a cool bath

  • Do NOT give fluids