The Impact of Extreme Heat on the Body and Who Is Most Vulnerable

Nearly 77 million Americans across the Midwest and Northeast are under heat alerts this week, with the National Weather Service warning of dangerously high temperatures, reaching the triple digits in many areas.

In Phoenix, temperatures are forecast to soar to 113 degrees on Thursday — the first day of summer — followed by 115 degrees on Friday.

According to the Centers for Disease Control and Prevention, extreme heat can be lethal. Heat-related deaths in the U.S. have been increasing over the past few years, with about 1,600 in 2021; 1,700 in 2022, and 2,300 in 2023, according to the Department of Health and Human Services.

As temperatures are expected to scorch parts of the U.S. this week, here’s some important information on what extreme heat can do to the body, who is most at risk, and the heat-related illnesses to watch out for:

 Effects of Extreme Heat on the Body

A normal human body temperature ranges from 97°F to 99°F. The body’s temperature needs to be regulated for internal organs to function properly. When your brain senses a change in body temperature, it tries to help your body readjust.

When the body’s temperature is too hot, it commonly cools itself through sweating, which then evaporates, thus cooling the body. The body also cools itself by moving warmer blood away from the internal organs to capillaries at the skin’s surface, which is why people look flushed when overheated.

Heat-related illnesses can set in when the air temperature is hotter than the skin’s temperature, around 90°F, making it harder for your body to cool itself. In extreme heat combined with humidity, sweat doesn’t evaporate as easily, causing body temperature to rise even higher, according to the Mayo Clinic.

Who Is Most Vulnerable to Extreme Heat?

According to the National Institute of Health and the CDC, the following groups are most at risk in extreme heat:

• Children: Their bodies regulate internal temperatures differently, making them more susceptible to heat.
• Older adults: More likely to have chronic conditions or take medications that affect the body’s response to heat.
• People with chronic medical conditions: Less likely to sense and respond to temperature changes.
• Pregnant people: Their bodies must cool down for both themselves and their developing babies.
• People experiencing homelessness: More exposed to extreme heat due to lack of shelter.
• Athletes and outdoor workers: More likely to become dehydrated and develop heat-related illnesses from strenuous outdoor activities.
• Pets: Also susceptible to heat-related illnesses.

For information on cooling centers in your state, the National Center for Health Housing provides a list.

Heat-Related Illness Symptoms to Watch For:

The Centers for Disease Control offers guidance on recognizing and preventing heat-related illnesses such as heat stroke, heat exhaustion, heat cramps, sunburn, and heat rash. Key symptoms to watch for include:

• Heat stroke: High body temperature, confusion, rapid pulse.
• Heat exhaustion: Heavy sweating, weakness, cold, pale, and clammy skin.
• Heat cramps: Muscle spasms usually in the legs or abdomen.
• Sunburn: Painful, red, and warm skin.
• Heat rash: Red clusters of small blisters.

Understanding these symptoms and taking proactive measures can help prevent heat-related illnesses during extreme heat conditions.