Many people enjoy outdoor workouts as a chance to get fresh air, sunshine, and perhaps spend time in nature.
Exercising in high temperatures can be dangerous, as it can lead to heat-related illnesses like heat cramps and heat exhaustion.
Symptoms of heat exhaustion include nausea, vomiting, weakness, dizziness, fatigue, headache, and excessive sweating.
Tips for how to exercise in the heat safely include staying hydrated, starting gradually, knowing your limits, wearing the right clothing, and listening to your body.
If you enjoy outdoor exercise—like going for a morning jog or a lunchtime bike ride—you can feel good knowing you’re taking charge of your health. You’re out in the fresh air and moving your body. Plus, if you’re spending time in nature, that supports your mental health, too.
However, exercising in the heat poses certain dangers to your well-being, and you’ll want to proceed with caution. You don’t need to avoid outdoor workouts in the summer, but you do need to stay safe while exercising in hot weather.
Want to know how to exercise in the heat? Read on for safety tips on how to stay cool when working out in hot environments.
Is It Better To Exercise In The Heat?
If you’re inside, you might be tempted to try hot yoga (or similar heated fitness classes). Here, your workout takes place in a hot environment, with a high temperature of 90-105 degrees Fahrenheit or more.
If you’re outside, warmer weather means you don’t need to worry about wearing a jacket, getting caught in a blizzard, or slipping on an icy sidewalk.
Here are a couple of myths and realities of exercising in the heat:
Myth: When you exercise in the heat, it helps you lose body weight. Reality: Any weight loss is probably due to fluids lost through sweating. Plus, when your internal body temperature increases, it typically burns carbs instead of fat. 
Myth: Heavy sweating detoxifies your body. Reality: Your liver and kidneys handle most of your body’s detoxification. Excessive sweating causes you to lose nutrients like calcium, potassium, and sodium, and can lead to dehydration. 
While heat training can work for an athlete whose goal is “heat acclimation” (i.e., helping the body acclimate to a hot environment), the negatives of exercising in high temperatures outweigh any benefits for most people.
What Are The Dangers Of Exercising In The Heat?
Working out in hot weather—especially extreme heat—brings a special set of dangers to worry about. Summer heat, especially paired with high humidity, can raise your core body temperature. The body tries to cool itself by circulating more blood through your skin. But, as a result, this can raise your heart rate because it decreases the blood flow your muscles need.
If you’re engaged in physical activity (especially if you’re out in direct sunlight), this can further impact your body heat. With high humidity, your sweat doesn’t evaporate as fast and your body can’t release heat as quickly as it needs to. This can lead to a variety of heat-related illnesses. 
As your first warning sign that you’re overdoing it, you might experience heat cramps. These muscle pains or spasms often occur during intensive exercise accompanied by heavy sweating.
This more severe heat illness can occur after spending extended time in a high temperature and having inadequate fluid intake. Symptoms include nausea, vomiting, weakness, and more.
What Are The First Signs Of Heat Exhaustion?
Heat exhaustion is serious heat-related illness. It happens when your body temperature gets too high, and your body is not able to quickly cool itself down. If you don’t treat it, heat exhaustion can lead to heat stroke—which can be fatal. Pay attention to these telltale symptoms: 
Physical weakness is a lack of muscle strength and is a sign that the high temperature is affecting your body and that your heart may not be pumping enough blood. You should relocate to a cool, shady place if possible and avoid further outdoor exercise.
Fatigue is when you feel tired and have a lack of energy. Try to reduce your physical activity and find a place to cool off.
If you are suffering from heat exhaustion, you might experience headaches. This is your body’s signal that you are dehydrated, which can be common when you are overheated and not drinking enough fluids.
Heavy sweating is a sign that your body temperature has risen, and your sweat glands are activated to try to cool you off. However, in environments with high humidity, your body cannot effectively use sweat to cool off. It’s important to stop your activity and move to a more cool environment.
Dizziness or lightheadedness
If you feel dizzy or lightheaded, then it’s a sign you may have reduced blood flow to your brain because of the hot environment. You need to sip water and relocate to a cool place where you can rest.
Heat cramps are muscle pains, especially in the abdomen, arms and legs, that can happen when you are overheated. If you have muscle cramps, you need to halt your exercise, drink fluids, and rest.
Nausea or vomiting
If you are throwing up, you need to get medical attention right away.
How To Stay Cool And Safe When Exercising In The Heat
Just because the heat index is rising during the summer doesn’t mean you need to ditch your outdoor workouts. However, you can follow these warm-weather workout safety tips to prevent a heat-related illness. [3,4,5]
Sweating is your body’s way of cooling itself. But when you sweat, you also lose fluids. And if you don’t continue to replace those lost fluids, you’ll get dehydrated. When this happens, your core temperature rises, which can put your organs and nervous system at risk.
That’s why it’s important to drink lots of cold water before, during, and after your workout to stay hydrated. Also, consider drinking sports drinks to help replace sodium, potassium and electrolytes you’ve lost.) When working out in the heat, hydrate every 15 minutes—even if you’re not thirsty—with a goal of 16-32 ounces of fluids every hour.
If you typically work out indoors or in cooler temps, go easy when first start an outdoor exercise routine. It can take a minimum of one to two weeks for your body to adapt to the heat. As your body slowly gets acclimated to the hotter weather, gradually increase the exercise intensity and duration.
Wear light, breathable clothing
You want clothing that allows moisture to evaporate quickly and enable your skin to cool, so wear loose-fitting, light-colored, lightweight clothing. Some athletic clothing is now made from moisture-wicking fabrics to help keep you cool while exercising. If you’ll be out in the sun, wear a wide-brim hat, sunscreen, and sunglasses to keep cool (and protect yourself from harmful UVB rays).
Know the signs
Pay attention to your body’s cues when you’re working out in the heat. If you start noticing any of those telltale symptoms (dizziness, nauseous, or fatigue), then take a break—in a cool environment if possible. It’s better to rest than overdo it and end up with a heat-related illness.
Know your limits
If you're not in good shape or you’re an exercise newbie, understand (and respect) your fitness limitations. Use extra caution when working out in hot temperatures and take frequent breaks.
Even if you’re in great shape, you might not be used to exercising in hot weather. This isn’t the time to set a new personal best! Instead, reduce your exercise intensity and shorten your workout duration.
Keep in mind that, when exercising outdoors, you should always wear sunscreen to avoid the harmful effects of the sun’s radiation.
If you’re like many people, you enjoy exercising outdoors as a way to get fresh air, sunshine, and spend time in nature. However, exercising in high temperatures can be dangerous. In fact, it can lead to heat-related illnesses such as heat cramps and heat exhaustion. If left untreated, heat exhaustion can lead to heat stroke—a life-threatening emergency. Symptoms of heat exhaustion include nausea, vomiting, weakness, dizziness, fatigue, headache, and excessive sweating. Tips to stay safe and cool include staying hydrated, starting gradually, know your limits, wear the right clothing, and listen to your body. With these tips in hand, you know how to exercise in the heat safely.
Continue to check back on the Nature Made blog for the latest science-backed articles to help you take ownership of your health.
This information is for educational purposes only and is not intended to serve as medical advice or a recommendation for any specific product. Consult your health care provider for more information.
Lisa Beach is a seasoned journalist whose work has been published in The New York Times, Good Housekeeping, Eating Well, Parents, AARP’s Disrupt Aging, Optimum Wellness, and dozens more. She also writes for a variety of health/wellness-focused brands. Check out her writer’s website at www.LisaBeachWrites.com.
Amy has an MFA in Creative Writing from Antioch University in Los Angeles and is a credentialed English teacher, though she left the classroom to write full time. She especially enjoys creating educational content about health, wellness, and nutrition. Her happy place is in the kitchen, and when not writing, you can find her trying out “kid-friendly recipes” and “healthy desserts for chocolate lovers” from her Pinterest board.
Lynn is a Registered Dietitian (R.D.) and is a member of the Medical and Scientific Communications team at Pharmavite. She has over 20 years of experience in integrative and functional nutrition and has given lectures to health professionals and consumers on nutrition, dietary supplements and related health issues. Lynn frequently conducts employee trainings on various nutrition topics in addition to educating retail partners on vitamins, minerals and supplements. Lynn has previous clinical dietitian expertise in both acute and long-term care, as well as nutrition counseling for weight management, diabetes, and sports nutrition. Lynn earned a bachelor’s of science in Nutrition with a minor in Kinesiology/Exercise Science from The Pennsylvania State University. She earned a M.S. degree in Human Nutrition from Marywood University in Scranton, Pennsylvania. Lynn is an active member of the Academy of Nutrition and Dietetics, Sports Cardiovascular and Wellness Nutritionists, Dietitians in Functional Medicine, and holds a certification in Integrative and Functional Nutrition through the Academy of Nutrition and Dietetics.