BY THE OPTIMIST DAILY EDITORIAL TEAM
Summer sun often feels like an open invitation to move your body outdoors. And actually, many people prefer it that way. According to a OnePoll survey for the fitness app Verv, 75 percent of men and over half of women said they’d rather exercise outside. With benefits like increased motivation, lower stress, and improved mood, it’s easy to see why nature beats the treadmill for many.
But as temperatures rise, so does the need to approach workouts with more care. A hot summer doesn’t just mean extra sweat. It means real health risks, especially during heatwaves or extreme humidity. Whether you’re training for a race or enjoying a weekend hike, knowing how heat impacts your body can help you move smartly and safely.
What happens to your body in the heat
When you’re working out in high temperatures, your body engages in a process called thermoregulation, its way of keeping internal temperature in check. Heather Milton, CSCS, a clinical exercise physiologist at NYU Langone, explains that thermoregulation kicks in through increased sweat and blood flow to the skin. These changes help release heat, but they also make your body work harder than usual. That’s why the same workout feels more intense outdoors in July than it does in a climate-controlled gym.
This added effort increases your heart rate, which can leave you feeling exhausted more quickly. If you’ve ever done hot yoga and wondered why it felt like ten workouts in one, this is why: the heat is an invisible layer of extra resistance.
How heat affects recovery
The body’s cooling efforts don’t end when the workout does. Extra sweating and diverted blood flow can delay recovery. When fluids and electrolytes are lost, muscle repair and energy replenishment take longer.
Bethany Stillwaggon, a master coach at Row House, points out that elevated temps can lead to longer recovery times, headaches, muscle cramping, dizziness, and fatigue. Muscles rely on water and proper circulation to bounce back after exertion, and hot workouts can disrupt both.
Can your body adapt to working out in heat?
Yes—to a degree. Like any form of stress, your body can build tolerance to exercising in warmer conditions. Personal trainer Ally McKinney says that over time, your body learns to regulate heat more efficiently. That means heart rate, sweat response, and perceived exertion can all improve with consistent exposure.
However, conditioning has its limits. No amount of training can change the fact that extreme heat can overwhelm your body’s cooling systems. When that happens, risks increase.
When is it too hot to exercise?
Once the temperature climbs past 90 degrees Fahrenheit, it’s time to be extra cautious. According to Milton, 91.4 degrees is when the risk of heat exhaustion begins to rise. That’s the point where the body struggles to deliver enough blood to both the skin (for cooling) and internal organs.
At 92 degrees and up, your core temperature can reach dangerous levels. Milton warns that this can lead to heatstroke, which includes serious symptoms like confusion, dizziness, irrational behavior, and even collapse. This is a medical emergency and requires immediate cooling.
To avoid danger zones, aim for early morning or evening workouts when it’s cooler, or bring your movement indoors on high-heat days.
How to stay safe during hot workouts
The number one rule? Hydrate. Dr. Jennifer Haythe, cardiologist and director of cardio-obstetrics at New York Presbyterian Hospital Columbia, recommends drinking two glasses of water before exercise and continuing with four to six ounces every 20 minutes during your workout. And of course, rehydrate afterward.
Hydration isn’t just about water. Sweating depletes key minerals like sodium and potassium, both critical for muscle function and cellular processes. Sports drinks with electrolytes can help; just aim for about 14 grams of carbohydrates, 28 mg of potassium, and 100 mg of sodium per 8 ounces. You can also get those nutrients from food like bananas, olives, cottage cheese, and beets.
Milton adds that you may need up to 20 percent more fluid than usual when exercising in heat, and for every pound of sweat lost, replenish with at least half a liter of water.
Don’t skip the sun, just be smart about it
Outdoor exercise has undeniable perks, but hot weather requires thoughtful planning. When the forecast hits high numbers, listen to your body, hydrate well, and keep an eye on the time of day.
Heat can build strength, stamina, and resilience, as long as it’s met with preparation. With the right strategies in place, you can enjoy sunny sweat sessions without putting your health at risk.
