1. Let Your Body Acclimate to the Heat

No matter your fitness level, everybody needs time to acclimate to the heat. Failure to do so is actually a risk factor for heat-related illness (as are poor physical fitness and strenuous exercise), according to a study published in April 2019 in the journal American Family Physician.

“Heat acclimation lets the body get used to operating in higher temperatures and helps prevent the system from being shocked when training,” Dr. Olufade says. If you take this step, you’ll be able to exercise at a higher level for a longer time while maintaining a lower body temperature when the heat is up.

To do it (as the weather starts to change or if you’re traveling somewhere with much warmer temperatures than you’re used to), start with shorter workouts and gradually increase the duration and intensity over a period of 10 to 14 days, Olufade says. Until you’re acclimated, hold off on intense or long workouts in the heat.

2. Know Your Risk

Heat affects everyone differently owing to a variety of factors (age, genetics, fitness level, other health issues), but certain groups should take extra precautions. People who are generally at increased risk of heat-related illness include:

• Older adults
• People who don’t often work out
• People with preexisting health conditions like heart disease
• People with acute illness like fever and upper respiratory infections
• People taking certain medications, such as diuretics and COPD medications

If this is you, you’ll need to be extra cautious about exercising in heat. Sometimes it may be best to work out indoors with AC.

3. Don’t Forgo Pre-Workout Hydration

Staying hydrated is key no matter the time of year, but it’s even more important during hot conditions. If possible, drink more water two to three hours before exercising. On top of the 125 ounces (oz) and 91 oz of water men and women, respectively, should be consuming daily (according to the National Institute of Medicine Food and Nutrition Board), aim for six milliliters of water per kilogram of body mass before working out, Olufade says. Water is always an effective pre-workout beverage, but you can sip drinks with electrolytes to amp up the hydration.

One way to tell if you’re hydrated is to pay attention to the color of your urine (and whether you’re peeing about as much as usual). If you’re hydrated, it should look more clear than yellow, and you should be peeing about as much as usual.

4. Eat for Hydration

You can also increase your body’s hydration level by eating water-rich foods throughout the day, says Julie Brown, RD, an American Council on Exercise (ACE)–certified personal trainer and dietitian with Life Time in Chanhassen, Minnesota. Water-rich foods include cucumbers and watermelon.

5. Don’t Eat Too Much Beforehand

When working out in the heat, avoid eating a big meal before exercise. “Digesting food requires energy,” Brown says. Digestion creates more body heat, she explains, and pulls blood flow away from the muscles you’re working during exercise. If your body is trying to digest food and move vigorously at the same time, digestive discomfort can result, leading to a bummer of a workout.

6. Wear Heat-Appropriate Clothing

Wear clothing that allows heat to escape your body. “Loose-fitting, light-colored clothing is best for keeping the body cool,” Olufade says. Look for fabrics, often synthetic, that are lightweight and moisture wicking (it should say so on the label).

7. Use Sun Protection

Heat and humidity aren’t the only worry in the summer. Sun exposure is the leading risk factor for skin cancer; so take steps to protect yourself.

Slather on the sunscreen, choosing one with at least an SPF of 15, according to the Skin Cancer Foundation. Use two tablespoons for your entire body, applying it 30 minutes before you go out. Reapply every two hours, per the general guideline, but if you’re sweating, reapply every hour, according to the American College of Sports Medicine.

Also, consider clothing with ultraviolet protection factor (UPF), which is like SPF but for clothes and hats. And wear sunglasses that block 99 to 100 percent of UVA and UVB rays and screen out 75 to 90 percent of visible light, according to the American Academy of Optometry. Yes, you need to protect your eyes from the sun, too!

8. Carry Water (or Know Where to Find It During Your Workout)

When the temperature climbs above 80 degrees F, bring water with you (or plan ahead of time where on your exercise route you can find some).

You’ll need to replenish your body with 7 to 10 oz of water for every 10 to 20 minutes of exercise in the heat, according to ACE. And if your workout will last more than 60 minutes, consider adding an electrolyte supplement to your water (they help the body maintain fluid balance, which is important when you’re exerting yourself and losing a lot of water via sweat).

9. Avoid Middle-of-the-Day Workouts

“Midday sun can add about 20 degrees to the temperature [depending on where you live and time of year],” Brown says. That means midday is usually the hottest point of the day.

If you’re running, walking, or biking, choose a shadier route whenever possible, and avoid times when the sun is most intense, usually between 10 a.m. and 4 p.m.

10. Monitor the Air Quality Index (AQI)

Air quality is a growing concern in outdoor exercise. “Air quality impacts the exchange of oxygen in the lungs,” Olufade says, adding that people with asthma and allergies are at higher risk of having complications while exercising in poor air quality. “Your body functions better when the air quality is better.”

So when is the AQI (a combined measure of ozone, particle pollution, carbon monoxide, sulfur dioxide, and nitrogen dioxide) too high to exercise outdoors? Brown says that anything 50 or above (check local forecasts or AirNow for your city’s current air quality) can pose challenges for people with compromised health. Play it safe by choosing times of the day with a lower AQI or modify your plans by moving indoors or changing your intensity or duration.

11. Tailor Your Workout to the Weather

Don’t save your most intense workouts for the hottest days. Dial down the intensity level of your workout (opting for a lower-impact activity or shorter workout) when the temperatures and humidity are high.

Also, consider an activity that will allow you to take breaks to hydrate and let your heart rate fall, Olufade says. If you belong to a gym, do your warm-up and cooldown in the club so you cut your time in the heat, Brown suggests.

Risk of heat-related injury increases when the temperature climbs above 80 degrees F and the humidity is greater than 75 percent, according to the American College of Sports Medicine. Consider adjusting your workout in one of the above ways in those conditions.