How to Run In the Heat Without Dying

Extreme summer heat is becoming the norm. Don’t be a martyr.

It’s getting hot out here, huh? Texas is in the midst of a heat wave that’s pushed the heat index above 120 degrees in spots. Wildfires in Canada—the ones that turned NYC orange—are still contributing to high temperatures and smoky air across the U.S. And this is just the beginning: The National Oceanic and Atmospheric Administration (NOAA) is predicting 2023 could likely be one of the top 10 warmest years on record in a huge portion of the U.S. 

Even if you’re not engulfed in conditions that feel practically apocalyptic, running in the blistering summer heat and humidity can be dangerous. Understanding how to stay safe is what will help you turn your summer training into fall PRs. 

The most important thing to accept about running and racing in the summer is that your paces WILL change. There is an ideal temperature range for marathoning: It’s between 46°F to 59°F, a 2019 study published in PLOS One determined after analyzing nearly 50 years of finishes at the Boston Marathon (a race known for its erratic weather). 

So when the mercury creeps higher, paces do the same, according to older research from the International Journal of Biometeorology: For each 1.8°F increase in temperature above 59°F, runners who average 5:45 minute/mile pace or faster slow down by about one second per mile for each 1.8°F increase in temperature above 59°F, while runners who average 7:25 to 10:00 minute/mile pace slow down 4 to 4.5 seconds per mile. The more extreme the temperature change, the more effect it has on your pace.

Heat makes your core temperature rise. And when that happens, blood is shunted away from your working muscles and redirected to your skin to aid in cooling you down; that reduces the amount of oxygen your muscles get, which will slow you down. Plus, as your core temperature rises to the point of fatigue, your body will actually self-regulate and slow you down to reduce that temperature spike. 

The goal then, is to keep your body temperature from rising too high. One of the easiest ways to do that is slow down. Instead of obsessing over pace, look to heart rate or your rate of perceived exertion (RPE) to see if you’re at the right effort level for a workout. You may be running 60 seconds per mile slower than normal during an easy run, but you’re not losing fitness—your body is working just as hard to maintain that pace in more extreme conditions.

Of course, there are more dramatic methods to stay cool, like dousing yourself in ice mid-run à la Molly Seidel in the 2021 Tokyo Olympics. If you can’t find ice along your route, don’t skip the sprinklers: Misting your face can reduce your rate of perceived exertion, according to an older study published in the European Journal of Applied Physiology. Cooling the neck was also shown to help you run farther in the heat in research published in 2011 in Medicine & Science in Sports & Exercise, while head-cooling (picture Galen Rupp switching out his hat at every water stop during the Olympic marathon) resulted in a 51 percent improvement in exercise time to fatigue in a study published in Physiological Research.

There’s two things at work here: First, dumping cold water or ice on your chest/shoulders/back cools not just the skin, but the capillaries underneath, which cools your circulating blood. The more surface area you can cover, the better. Second, putting ice or pouring cold water on your head has a trickle-down effect, and research published in the Scandinavian Journal of Medicine & Science in Sports found that an impromptu cold shower benefited skin temperature, thermal sensation, and RPE. 

Dumping water on yourself is actually better than drinking it if your goal is cooling down, according to a 2016 study in Temperature. But that doesn’t mean you can skimp on hydration: In the heat, you lose more fluids and electrolytes, so replacing them becomes even more important. 

If you’ve got a hot race on deck, practice pre-cooling. You get an average performance boost of 3.7 percent from pre-cooling—which translates to 55 seconds in a 25:00 5K—when lowering your body temp before performing, one scientific review published in the journal Sports Medicine found. In fact, the scientists discovered an average performance boost of 3.7 percent from pre-cooling—that translates to 55 seconds in a 25:00 5K. You could wear an ice vest or stuff your shorts with ice packs, or you could drink a pre-race ice slurry, which was shown to lower pre-exercise body temperature and increase time to exhaustion (i.e. you can keep pushing for 50 minutes instead of 40 minutes before stopping) in the heat in a 2010 study in Medicine & Science in Sports & Exercise. 

What these methods are doing is slowing down the increase in core temperature caused by exercise, allowing more blood to go to the muscles instead of the skin for cooling. It also gives you a wider window between your starting point and the point at which the heat is going to start causing physiological problems—allowing you to work harder for longer.

The good news: Exercising in the heat will improve your VO2 max, lactate threshold, cardiac output, and plasma volume, according to research published in the Journal of Applied Physiology: Respiratory, Environmental and Exercise Physiology—all of which will translate to major fitness gains once the temperature starts to come back down. 

In the meantime, give yourself some grace and stay safe (even if that means staying inside on certain days). That patience will pay off come fall.

the rundown

ASICS Magic Speed 3
I didn’t run in the first two versions of this shoe, which got some mixed reviews, but maybe third time’s the charm? I’m a big Metaspeed Sky+ fan, and this was a responsive, carbon-plated trainer that I enjoyed swapping in during faster workouts. In addition to the plate, it’s got a full Flytefoam Blast+ midsole, an upper that feels like the Metaspeed, and a few more millimeters of drop (which I recently learned I prefer). I definitely wouldn’t use this as a distance racing shoe, but it’s fun for picking up the pace during training.

“The Gospel of Wellness,” Rina Raphael 
This book isn’t running-specific, but it really digs into the idea of commodified wellness and how self-care has become the “solution” to job insecurity, hustle culture, a failing medical system, and so much more. “We are prone to buying what we want to believe, and we want to believe in quick solutions,” Raphael wrote about halfway through, and this sentiment really resonated with me: So much of wellness (and fitness) requires patience and moderation, but we’ve been conditioned to rebel against that in search of an insta-fix. The main takeaway, for me, is one that I also try to stress in my reporting: When it comes to anything highly hyped in the health world, do your due diligence to find out whether it’s worth it or not.

Anxiety Slows Down Recovery 
Here’s another argument in the case against abusing running as a mental health coping mechanism: Runners with a high level of anxiety have a slower recovery, delayed return to running, and altered gait biomechanics compared to those with low anxiety, according to research published last year in PLOS One. It’s easy to underestimate the effects mental health can have on your fitness, which is why it’s so important to have regular, honest check-ins regarding where you’re at physically and emotionally during training. 

How Much Exercise Is Too Much? 
Speaking of using running as a coping mechanism: Jen Miller took on the topic of exercise obsession for Slate’s Good Fit column, examining how the endurance sport community in particular celebrates going to extremes, and at what point that crosses into self-harm. I think there’s a contingent out there that believes this is a “healthier” form of addiction, but I’m not sure any form of addiction can really be labeled healthy. I also think there are a lot of people who, like Miller, haven’t figured out where the “line between persistence and excess” is—to their own detriment. It’s a good read if you find yourself constantly chasing more.