From Our Experts

Exercising in Hot Weather: Tips to Prevent Heat Exhaustion

Originally published June 3, 2022

Last updated May 8, 2023

Reading Time: 2 minutes

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When is it too hot to exercise outdoors? Here are doctor-approved tips on how to avoid heat exhaustion when exercising in the summer heat.

Whether you’re running, biking or going for a power walk, it’s important to take extra precautions, as summer temperatures start to rise.

Experiencing a little extra perspiration is natural, of course. But when should you take a bodily cue to slow down, head indoors or call someone for help?

Jennifer R. Boozer, DO, a family medicine physician at Keck Medicine of USC, shares easy precautions to take — and ways to spot trouble — when exercising in the heat.

Q: How do you know if it’s too hot to exercise outdoors?

A: Generally, when the heat index (how hot it really feels when relative humidity is factored in with the actual air temperature) is over 90 degrees Fahrenheit, there is an increased risk of serious heat-related illnesses. The heat index should be used when determining if strenuous outdoor activities are safe.

Q: What are some tips to exercise safely in hot weather?

A: Try to avoid exercising outside between the hours of 10 a.m. to 3 p.m., because that’s generally the hottest part of the day, or move your workout indoors, if necessary.

It’s important to take frequent breaks for hydration and cooling, and you should avoid activity during severe heat or humidity.

Keep hydrated by bringing a bottle or jug of water with you, and take a drink every 15 minutes — even if you’re not thirsty. Consider rehydrating with an electrolyte-replacing sports drink after your workout.

As far as workout gear goes, stick with light-colored, loose clothing; sunglasses; and a hat for protection from the elements. And don’t forget the sunscreen.

Q: How do you know if you’re experiencing heat exhaustion or heatstroke?

A: Symptoms of heat exhaustion can include extreme weakness, lightheadedness, passing out, coordination problems, headache, abdominal cramps, nausea, vomiting, diarrhea and persistent muscle cramps. 

A person’s body temperature is usually between 97 and 99 degrees Fahrenheit. With heatstroke, the temperature following collapse is above 104 degrees Fahrenheit, and the person will have symptoms such as disorientation, headache or irritability. They may also have altered consciousness or even seizures.

A: Anyone experiencing any of the signs or symptoms of heat exhaustion or heatstroke needs immediate medical care. The most important steps are to call 911, remove all equipment and excess clothing and start cooling. Get the person into a cool spot, and spray the person with cold water from a shower or hose.  Alternatively, apply ice packs around the neck, armpits and groin. Another option is to apply wet towels to the body. Don’t wait for paramedics to arrive — every minute counts to start cooling.

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Anne Dullaghan
Anne Dullaghan is a freelance writer and editor.