Intense heat can make walking the dog feel unbearable—let alone running 26.2 miles outdoors. But as temperatures rise, marathon runners are trying to make their bodies more prepared for race-day conditions, according to Bloomberg.

Elite runners are increasingly using strategies like cooling apparel and changing their pacing to improve their ability to tolerate heat, the publication reported. Sub-three-hour marathoner Chris Dougé, a New York business developer training for the 2026 Chicago Marathon, told Bloomberg that he incorporates three sauna sessions per week into his training to prepare for the hot weather he’ll likely encounter on race day.

Of course, not everyone is competing at this level. But could everyday runners, hikers, cyclists, and others who exercise outdoors benefit from heat training, too?

Can You Really ‘Train’ For the Heat?

The short answer is yes. It’s possible for your body to physiological adapt to the stress of a hotter environment, said Meg Darmofal, DPT, a physical therapist at MSU Health Care. And the process even has a name: heat acclimation.

According to Darmofal, heat acclimation triggers changes across body systems that help the body more effectively:

• Cool itself down
• Regulate its temperature
• Lower heart rate
• Disperse heat
• Deliver oxygen

That might mean, for example, starting to sweat sooner and more efficiently or increasing blood flow to the skin and muscles, which can help cool the body down and boost performance.

The perks of heat acclimation go beyond simply feeling more comfortable while exercising in hot weather. It can also make working out in the heat safer, according to Harry Stafford Jr., MD, CSCS, a sports medicine specialist and associate director of the Duke Sports Science Institute.

“You’ve gotten yourself acclimated and able to handle your training so that you don’t get heat illness and heat stroke,” Stafford told HEALTH. “Your body also becomes efficient—your heart rate drops and there’s less strain on your cardiovascular system.”

What’s the Most Effective Way to Heat Train?

The best way to acclimate to the heat is to replicate the activity and intensity you’re preparing to do in hot weather, experts agreed. So if you like to walk around your neighborhood in the summer, for example, you might start in spring by taking shorter walks during the warmer parts of the day.

That means that things like hot tub and sauna sessions probably aren’t enough to fully prepare you for exercising in the heat (unless your exercise of choice happens to be, say, hot tub aerobics).

That said, some research suggests that saunas and hot tubs are warm enough to spur the physiological responses involved in heat acclimation.1 And using them before or after exercise may promote acclimation, Darmofal said, because they can help promote recovery “so that you can train harder the next day.”

So, Should You Heat Train?

According to both Darmofal and Stafford, heat training may benefit anyone who exercises in hot conditions, whether they’re lifting weights in the backyard or running 26.2 miles.

After all, “everyone’s body has a thermoregulatory system that responds to the environment it is within,” Darmofal told HEALTH.

If you’re interested in trying heat training, Darmofal suggested speaking with your doctor first about whether it’s right for you and how to do it safely based on your individual circumstances. Heat training isn’t safe for everyone, so it’s especially important to get your doctor’s approval if you fall into one of the following groups, according to Stafford:

• People with a heart condition
• People with sickle cell trait
• People with obesity
• People who are sedentary

When Should You Start Training?

If your doctor gives you the green light, research suggests starting heat acclimation one to three weeks before you expect to exercise in hot conditions.2

Darmofal recommended increasing intensity no more than every four days. Still, she emphasized that you should make decisions and adjustments based on how you’re feeling rather than trying to hit milestones on a timeline.

There’s also no universal timeline for becoming acclimated to hot temperatures, Stafford said. Factors such as fitness level, experience, and muscle and fat mass may all play a role.

However, research suggests that people typically begin showing signs of heat acclimation around the third day of training, including a lower heart rate and body temperature and more efficient sweating.23 By the fourth day, your tolerance for the heat will likely be higher.

“The benefits of heat training last longer in individuals who have trained over a longer time than those who have completed heat training in less time,” Darmofal said.

Those benefits usually begin decreasing after about two weeks without heat exposure, she added, and full acclimation is typically lost within a month.

How to Safely Train for the Heat

Anyone purposefully exercising in the heat should focus on one key element: hydration.

The more sweating you do, the more dehydrated you get, so replenishing lost fluid and electrolytes is crucial for safe and effective recovery, according to Darmofal.

Stafford recommends drinking 32 ounces of an electrolyte drink before 2 p.m. on the days you’re heat training. If you’re feeling extra motivated, weigh yourself before and after your workout to see how much fluid you need to replenish. His rule of thumb is 16 to 24 ounces of fluid for every pound you lose with exercise.

Your urine can also reveal your hydration level: the lighter the color, the more hydrated you are.

If you experience any of the following symptoms, you should stop your workout or sauna session immediately and seek medical attention, according to Stafford and Darmofal:

• Dizziness
• Lightheadedness
• Shortness of breath
• Weakness
• Fatigue
• Chest pain
• Nausea or vomiting
• Cool skin
• Headache

And keep in mind that you shouldn’t exercise outdoors when the temperature is 84 degrees Fahrenheit or higher, regardless of how acclimated you are, according to Darmofal. At 103 to 124 degrees, heat exhaustion or heat stroke are possible, and heat stroke is likely if you’re exercising outside at 125 degrees.4

“Avoiding the warning signs mentioned above and understanding the risks versus rewards of training in high temperatures are important for anyone who plans to train in heat,” Darmofal said.