Peloton member working out on the beach sweating

7 Tips to Stay Cool and Safe While Exercising in the Heat

Before you head outdoors for a sweaty summer run, learn what’s happening in your body and how to work out safely.

By Karen AspUpdated March 27, 2024

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Whether you’re heading outside for a walk or run with the Peloton App or taking to the pickleball courts, steamy summer weather can add an extra challenge to your outdoor workouts. Although working out in the heat and humidity may be beneficial to some, everybody needs to be cautious when exercising outdoors in warm weather.

What safety precautions should you keep top of mind, though? And how do you know when it’s too hot to exercise outdoors? Experts weigh in so you can keep yourself safe while still enjoying your favorite activities. 

How Heat Affects Your Workouts

If you’re a fitness enthusiast, one of the biggest reasons to celebrate warmer weather is being able to move your workouts outdoors. But if you’re not acclimated to the heat, research shows that heat stress increases the amount of work your anaerobic system has to do. This can make your workout feel more difficult than it would in a temperature your body is used to. In fact, according to participants surveyed in The Peloton Report: Spring Wellness Trends, extreme heat (41 percent) and weather conditions (60 percent) were among the biggest obstacles to participating in outdoor fitness.

You’ll also likely sweat more in the heat—an average of 1 liter per hour, to be exact—which is your body’s way of cooling itself down. Of course, if you’re not properly replacing the fluid lost through sweat with proper hydration, your blood volume will decrease making it more difficult for your body to maintain its core temperature.

So what can you do to make exercise in the heat feel easier? Here are seven strategies for logging a sweat when the mercury is climbing:   

7 Tips for Exercising in the Heat

1. Give Your Body Time to Acclimate

Individuals who are fitter tend to tolerate heat better, but regardless, your body still needs time to get used to that heat. When you first start exercising in the heat, lower the intensity and duration of your workouts. Within seven to 14 days of doing continuous or intermittent aerobic workouts, your body should be acclimated, according to the University of Colorado Hospital in Denver.

2. Adjust Your Workout Time

Plan to work out first thing in the morning or later in the evening to avoid the heat of the day. “The hottest temperatures happen in the mid-afternoon hours between 2 and 6 p.m.,” says Bruce Jones, a meteorologist at Midland Radio Corporation in Kansas City, Mo. But that’s not all. The Skin Cancer Foundation also recommends staying out of the sun between 10 a.m. and 4 p.m., when the sun’s rays are the most intense, to avoid sun damage. If you’re usually a midday exerciser, adjusting your workout time can help you adhere to both guidelines.

3. Modify Your Workout

If you can’t adjust your workout time, at least adjust your intensity. For instance, when Peloton instructor Becs Gentry can’t slide in an early morning run, she’ll walk outside later instead, lowering the intensity so that the heat doesn’t sap her.

4. Plan Your Routes

Whether you’re walking, running, or cycling, choose a route that’s more shaded and breezy on days when that heat could be problematic, Becs says, like a tree-lined street or along the water. And think about where public water fountains are. “I always run routes in New York City with water fountains along them so I know I can grab water regularly,” she says.

5. Stay Hydrated

Hydration is key, no matter what time of year it is, but it’s especially important that you don’t overlook your hydration needs in summer, says Gina Lovenitti, an exercise physiologist at Carda Health. While hydrating during your workout is crucial, you need to start before you exercise. According to the National Athletic Trainers’ Association, you should drink 500 to 600 ml of water or a sports drink two to three hours before exercising and another 200 to 300 ml of the same 10 to 20 minutes before you exercise (236 ml is one cup). During exercise, you need to make sure that you’re replacing water lost through sweat (and urine if you stop for a bathroom break) so that you’re keeping your body weight loss to below two percent. For most people, this means sipping 200 to 300 ml of water every 10 to 20 minutes.

6. Dress Appropriately

Wear moisture-wicking clothing, preferably in colors that are light. You might even look for workout clothes with an ultraviolet protection factor (UPF), which indicates how much of the sun’s UV rays can penetrate that fabric. For instance, a UPF 50 means that only 1/50th of the UV rays can potentially reach your skin, according to the Skin Cancer Foundation. To stay protected from the sun, wear UV-blocking sunglasses and a hat or visor. (And of course, apply a broad-spectrum sunscreen with an SPF of 30 or higher every 2 hours.)

7. Know Your Limits

If you start feeling dizzy or nauseous, stop exercising immediately, Lovenitti says. That’s a sure sign the heat is too much for you and may even be a sign of heat exhaustion or heat stroke. If you plan to exercise in the heat, learn to recognize the signs and symptoms of heat-related illness as laid out by the CDC and, as with any time you plan to exercise outdoors, tell a friend or family member where you’re going and when you plan to be back, in case of emergency.  

Benefits of Exercising in the Heat

The negative consequences of exercising in the heat can’t be overstated. “Exercising in hot and humid conditions always increases the risk of dehydration and heat illnesses like heat stroke,” Lovenitti says.

That’s not all, of course, as you could easily sweat off the sunscreen you’ve applied, putting you more at risk of developing a sunburn or sunstroke, Becs says. You may even get more chafing on your skin “With extra salt on your skin from the sweating, you may find that your workout gear suddenly chafes,” she explains.

Yet might there actually be some benefits to exercising in the heat? Yes, depending on your fitness level and goals.

For starters, if you’re competing in a race that will take place in hot weather, you need to train your body to get used to exercising in the heat. Doing so will help improve your performance, Lovenitti says. And if you’re an athlete who’s looking for performance increases, exercising in the heat can help you get comfortable with being uncomfortable quickly, she adds.

When to Move Your Outdoor Workout Indoors

As much as you may love exercising outdoors, there are times when it’s simply too hot to be active outdoors. To determine this, check the weather first, paying attention to something called the heat index. That takes into account temperature and relative humidity to measure how hot it really feels outdoors.

That’s key because when the relative humidity is high, your body will have trouble regulating its temperature and you’ll feel a lot warmer, according to the National Weather Service (NWS). So how hot is too hot? When the heat index is between 80 and 90 degrees Fahrenheit, you’re urged to use caution, as you could experience fatigue with “prolonged exposure and/or physical activity,” per the NWS’s heat index chart. Use extreme caution when the heat index is 90 to 103 degrees Fahrenheit. Anything above that is considered dangerous. Or simply put, “On days when heat advisories, air quality alerts, or excessive heat warnings have been issued (by meteorologists), it’s healthier to exercise indoors,” Jones says.

Check-in with yourself, too. If you’re hungover, for instance, you’re no doubt dehydrated, which could increase your risk for a heat-related illness if you were to exercise outdoors, Becs says. 

There are also certain populations who should avoid exercising in high heat and humidity. They include anybody who has high blood pressure or is pregnant or elderly, Becs says. If you’re unsure, check with your doctor before exercising in the heat.

If you move your workout indoors, just remember that hydration is important no matter what.

This content is for informational and educational purposes only and does not constitute individualized advice. It is not intended to replace professional medical evaluation, diagnosis, or treatment. Seek the advice of your physician for questions you may have regarding your health or a medical condition. If you are having a medical emergency, call your physician or 911 immediately.

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