Everything You Need to Know About Running in the Heat This Summer

Summer training ain’t easy. With skyrocketing temperatures, high humidity, and scorching sun it can feel like it’s impossible to get in a good run.

Running in the Heat

A long run or fast workout is hard enough. What about a RACE? Like a friend of mine always says: In the heat, I don’t compete!

Even if you just run easy and skip the hard workouts, how are you even supposed to just feel good when running in the heat and humidity of summer?

In the last few weeks, the runners I coach have said some funny things about running in the heat. My favorite:

“I just got back from my 8-miler, and it was BRUTAL. I couldn’t do the workout… my body just isn’t ready for 90 degrees “feels like 95” at 6pm. I just tried to repeat to myself “I LOVE SUMMER!” while also being glad I wasn’t jumping over piles of snow.”

Training well through the heat and humidity of summer takes a careful approach that combines timing, gear, and an understanding of why exactly it’s so damn hard to run in the heat in the first place.

But of course, it will still be tough. A few weeks ago at the Heartbreak Hill Festival put on by Runner’s World, I was talking to another runner about a race she ran in Miami. She was lucky to meet Kara Goucher and Shalane Flanagan (two pro distance runners), who told her: “I’ll take running at altitude over running in Miami any day!

Even the pros hate summer running!

Instead of complaining about how difficult it is to run in the heat, let’s see how we can make the best of it. And maybe even make the fall our fastest season yet.

Why is it So Hard to Run in the Heat?

If you’ve read Christopher McDougall’s fantastic book Born to Run, you’ll remember that humans are amazing endurance animals for a host of reasons. We have:

  • A huge Achilles tendon that produces a significant energy return while running
  • A (mostly) hairless body and highly evolved sweat system
  • Big butts. I cannot lie: according to Harvard professor Daniel Lieberman, our glutes are “running muscles”
  • A special ligament that attaches the spine to the skull and keeps our head from bobbing as we run

Can you guess which adaptation here is impacted by running in the summer? It’s our incredible sweat system.

Perspiration helps cool us off because as our sweat evaporates from your skin, it takes heat with it. But when humidity rises, it reduces your body’s evaporation rate because there’s already so much water in the air. Soon, you feel overheated and have to slow down.

If you live in an arid place like Colorado where the humidity is low, a hot summer day can still wreak havoc on your training for two important reasons.

First, the dry air evaporates sweat from your body almost as quickly as you’re producing it so you can become dehydrated much more quickly. If you start a run slightly dehydrated or run long without any fluids, your performance will significantly decrease (and you’ll feel like death).

As you become more and more dehydrated throughout a run, your heart needs to work harder to pump your blood because it’s becoming thicker (among a few other reasons too). This is called cardiac drift: your heart rate increases over the course of a run even when the intensity stays the same.

Let’s not also forget the heat and sun, both of which increase your core body temperature. As soon as you start getting too warm, running will feel much more difficult. Your “Rate of Perceived Exertion” (RPE) will increase even if you’re running a pace that’s usually comfortable.

Less evaporation because of higher humidity levels, increased chance of dehydration, and a higher core body temperature means that you’ll have to run slower to maintain the same effort. An unfortunate reality of summer training.

The Dangers of Running in the Heat

Summer Running

This article isn’t meant to scare you. After nearly 16 years of competitive racing and running in the heat and humidity of New England and the mid-Atlantic states, I’ve never been seriously affected by the heat in any meaningful way. Neither has any of my teammates in college and high school – and we raced and ran very tough workouts in brutal temperatures sometimes.

But that doesn’t mean the dangers aren’t real. If you run too hard at noon in July, you might experience some type of heat illness. Here’s what you need to know so you can avoid these setbacks.

Heat Cramps: muscle spasms that are caused by large fluid and electrolyte losses from sweating. They can occur while exercising but also hours after your run. No need to worry, they’re not serious – but make sure you stay hydrated and get enough electrolytes with sports drinks or fruit like bananas.

Severe dehydration: we’re all familiar with dehydration. Up to a 4% loss in fluid levels from exercise is still safe, but any more than that and you may experience dizziness, fatigue, and even mental disorientation.

Prevent this level of dehydration by starting your run already hydrated (your pee should be a straw color) and replacing your lost fluids as soon as you finish running. You can figure out exactly how much fluid you’ve lost by weighing yourself before and after a hot run.

Heat Exhaustion: if you work out too hard in the heat, you may come down with heat exhaustion – a case of dehydration, headache, nausea, and a core body temperature of up to 104 degrees. It’s much more common in runners who aren’t adapted to the heat.

If you think you have heat exhaustion, stop running, get out of the sun, and cool down with a cold drink and preferably air conditioning. And next time, run earlier in the day!

Heat Stroke: Danger! Heat stroke is very serious since your core body temperature is probably over 105 degrees. Symptoms include disorientation with clumsiness, confusion, poor balance, and a lack of sweating. Immediate medical attention is required where you’ll be cooled with a cold bath, air conditioning, and cold liquids.

At the 1978 Falmouth Road Race, Alberto Salazar (two-time winner of the NYC Marathon) suffered heat stroke and collapsed at the finish line after fading to the 10th place. He was rushed to the hospital with a temperature of 107 (!) degrees and read his last rites in a tub of ice water. He recovered and went on to become one of the greatest coaches our sport has ever seen.

7 Tips to Beat the Heat

The heat of summer isn’t the time to run your hardest workout and biggest mileage weeks – unless you’re super careful.

Run by effort, not pace. Running in the heat is the perfect opportunity to work on the skill of running by feel. Instead of strictly following pace targets that you might normally follow, run by time and effort rather than distance and pace.

Run early. There’s no perfect time to run in the heat of summer. But the early morning hours offer the lowest temperatures and a break from the strongest hours of sunlight (even though the humidity will be at its highest).

Get off the roads! Asphalt and concrete absorb heat and radiate it back onto your poor, wilting body. The summer months are a good time to try more trail running. Bonus: you have to run a little slower on trails which will keep you slightly cooler and trails are usually shaded. Win-win.

Adjust your expectations. If the National Weather Service issues a heat advisory (when the Heat Index, a score that reflects a combination of both heat and humidity, is over 105 degrees) running fast or long will be difficult and dangerous.

Even if there’s no heat advisory, remember why it’s so hard to run like you normally do in summer weather. Maintain the same effort and don’t sweat the slower paces (see what I did there?).

Don’t wear dark colors or cotton. Gear matters in extreme conditions so dress appropriately! Synthetic fabric like polyester is used in most running gear these days – use it.

Start your run hydrated (and keep hydrating). Even though hydration has been overemphasized in the last decade (see Waterlogged by Dr. Tim Noakes), it’s important to hydrate well before and after your run. Unless you’re running more than 75-90 minutes, you probably don’t need to take any water with you. But learn what works for you.

Plan your run around water. I never carry any fluid with me on a run – even a 20 miler in the summer. Instead, I run by fountains in public parks where I can swig some water and stay hydrated. If you live in a dry climate, running through sprinklers can help you stay cool, too. And who doesn’t love frolicking through a sprinkler?

Running in the Heat Has Its Advantages!

With all the whining we do about summer training, it actually makes you a better runner. Running in the heat causes our body to acclimatize to the conditions and adapt:

  • Your body gets better at sending blood from your core to your skin, helping to dissipate heat
  • With all that blood rushing to your skin, your muscles now get less oxygenated blood. So to compensate, your body produces more (who needs blood doping?!)
  • The body learns to control its core temperature and it won’t increase as much after you’ve acclimatized
  • You start sweating sooner at a lower body temperature to improve the cooling process
  • Sweat contains less salt so you maintain the right electrolyte balance

All these adaptations improve your efficiency and make you ready to run even faster as soon as the heat and humidity drop in the fall. So embrace the heat and run through it!

Then again, there’s some evidence that suggests that summer training is difficult because you think it will be difficult.

Yeah, tell me that after I shuffle home from a track workout in the sun and I might throw you out of my living room window.

But, it’s useful to know that at least some of the drudgery of running in the heat is because of our brain. It may present a good opportunity to “train your brain” to be comfortable being uncomfortable.

When you do, you’ll be in a good position to run a lot faster this fall. Take advantage of the physical AND mental adaptations you’ve gained from a summer of uncomfortable running.

You might just surprise yourself at what you’re able to run in a few months!

Download the Summer Training Infographic!

I created a fun infographic as a reminder of how to stay cool when running in the heat this summer. Feel free to print it out or embed it on your own site.

Click here to tweet this infographic!

Running in the Heat

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  1. Lindsay Knake says:

    Cross training is another smart summer option when it’s dangerous to run.

    Two years ago in Michigan, we had a crazy hot summer (for us) with weeks of weather above 90 degrees and into the 100s with high humidity. We Northerners are not used to that. When the temperatures climbed above 100 degrees, I got on my bike instead of running. It felt cooler, it’s easy to bring along fluids along and the exercise wasn’t as hard on my body, but still allowed me to get in a good workout. I am grateful to have that option.

  2. Hi Jason: Can you also talk a bit about over-hydration? I just heard a story about a person who ended up in the hospital after running a marathon in California. The day was hot and she kept drinking (water? sports drinks? I’m not certain) throughout the race. Does this sound realistic?

    • Right, this is hyponatremia and usually happens when you run for 4+ hours and over-hydrate. Your blood sodium levels get diluted so much that it becomes very dangerous, sometimes fatal. Hyponatremia is more serious than dehydration which is why I only recommend hydrating on runs more than 75min in the summer. It’s ok to get dehydrated as long as you rehydrate after the run.

  3. Good tips! To help make sure I’m running at an easy pace I use a HR monitor to keep it honest. On hot days, I pay more attention to the dew point. If dew point >65, I know the conditions will be tougher so I set my pace and expectations accordingly.

  4. Jason,

    Any advice to tell my HS son whose coach seems to completely ignore the affects of heat and humidity? He’s using race times from the track season (when the temps were in the 50Fs) and plugging them into the calculators to get training paces. He’s “expecting” the runners to hit these training paces when it’s now in the 80s and much more humid.


  5. One thing a former coach used to tell us was to remember that our competition had to deal with the same conditions we did (assuming we were competing against a local field). So if we couldn’t train as hard as we normally would due to adverse weather, our competition likely couldn’t either. It was helpful in not feeling like we had to push ourselves as hard as we normally would and instead to train smart under the conditions.

  6. Thomas Slawson says:

    If it’s a really hot day and I have a longer run to do I split it up. If I’m doing 10 miles I’ll perhaps run 5 in the morning and 5 in the evening. Or if I’m feeling okay I’ll do 5 early, come inside in the air conditioning for about an hour and cool down then go outside and do another five.

    Also, every person is different when it comes to sweating. I sweat profusely and need a lot more fluid than my wife typically does. It’s important to know your own fluid needs.

  7. I trained for my first marathon last year in the Phoenix summer and it can be done! One thing that was absolutely crucial for was was hydrating during the run with cold water. On runs longer than 13 miles, I would break it up into two laps so I could come home, change my shirt, and get more cold water. Also buy an insulated water bottle.

  8. One trick I’ve used to stay a little bit cooler when it’s brutally hot out: roll up a few ice cubes in a bandana, then tie the bandana around your neck. The ice melts pretty quickly, but it feels great for the first 20 minutes or so!

  9. Great advice Except on water-if the average runner doesn’t take water except on long runs (75+ minutes) in the South Alabama heat and humidity it will not turn out well-I won’t go without water even for 30 minutes, even if just to pour it on body…Don’t leave home without it!

    • If you start a run hydrated, you can’t get significantly dehydrated in 30 minutes. Do what works for you, but be aware over-hydration is a bigger problem than dehydration.

      • Jennifer says:

        What about using some electrolyte brews for those shorter runs. I sweat sooo much, I feel I need fluids on most of my summer runs…. Prob not the 30 min runs but definitely if 6+ miles or really tough runs. Yesterday the temp was around high 60s but pretty humid. I ran 7 miles and by the end my shoes were so full if water from sweat dripping down my legs it was like I had run through a stream. I drank 20 oz of Gu Brew during that run. Any thoughts are appreciated!

  10. This is always a good reminder, since it can be so frustrating to run in the heat. I live in Florida, so there are days I give myself a break and use the treadmill. I plan my runs around drinking fountains and start long runs before 6am. Here, the heat is relentless. I keep reminding myself that I’ll see the results in the fall, but it is hard to be patient.
    One thing that has helped a lot is increasing my sodium and potassium intake . I definitely get headachy after long runs if I’m not careful. Coconut water is very high in potassium, which has been great for long run recovery, to help retain the water I consume midrun.
    And, one mental trick a friend of mine uses is to imagine yourself absorbing the energy from the sun and using it to keep going. It helps. 🙂

  11. Thanks for the tip. It’s been getting fairly hot here in Tokyo where I am, and I can only expect higher temperature and more humidity. Luckily, I run along a river near a bay so I get wind, which helps a lot. But believe it or not, I still see runners wearing long sleeved shirts underneath a shirt and long pants underneath a pair of shirts. I get hot just looking at them.

  12. For those of us who carry water on our long runs I always fill my hydration bottles half full and freeze them the night before my run. In the morning I fill them with water and it keeps the water fairly cold throughout my run as the ice melts. I do this with my gatorade as well. For me it has worked well.

  13. A few years ago when I was travelling in Laos, I made the mistake of going for a run without finding out about the area properly and underestimating the heat. I set of at 10:30am and was heading for a waterfall that I was told was 15km away, the plan being to run to the waterfall, have a swim and get a taxi back. However, it turned out to be well over 15km, causing me to run well into the middle of the day when the sun was the strongest. Long story short, I ended up with heat exhaustion and barely made it to the waterfall. After a long rest and plenty of fluids I started to feel somewhat normal though I was pretty exhausted for the rest of the day!

  14. Mike May says:

    Jason, thanks for the heads up on Summer running…Thankfully, I’ve adjusted to the heat in exactly the recommendations you prescribe. Actually, I enjoy running in the heat of the day here in Alabama. I’m 56 yrs old and make absolutetly sure of proper hydration and electrolyte intake before and during my 3 – 10 milers….It’s a slow pace but it sure makes the COLD beer taste that much better!!

  15. Water, water, water! Ultimately, it’s about staying in shape (and in summer, staying alive), not being a hero out there by trying to set a personal best in 100 degree heat!

  16. great tips . thanks for sharing the article. know your body and how far you can go too. don’t overdo it.

  17. I was starting to feel really discouraged about training for an october marathon because I have been miserable with the heat and mostly the humidity. I wasn’t hitting a target pace, and was even stopping to walk if it came to a hill.
    This article was VERY encouraging and helps me keep focused despite my slower speeds and zapped energy.
    Thank you!

  18. We just came across your great article!! Nice work! We thought you might like to know about our revolutionary new product that will help out with the heat…Kryoskinz Cooling Patches (kryoskinz.com). We’re a small startup striving to help athletes everywhere beat the heat and suffer smarter! Check us out!

  19. great tips. I really notice the difference in my performance when I run while interstate in more humid climates. Adjusting your expectations is important as I was getting annoyed at myself when I couldn’t achieve the same performance as in my home state, but its the weather, not me! 🙂
    Oh and I always have water near by, I love to sip!

  20. It’s so true, my performance is at about a 3rd of what it is in winter. The feeling I get is of intense strain in the chest area. Like my heart is having to pump treacle, which sounds almost right considering what you stated about dehydration.

    I don’t think it’s just a matter of taking a drink with you either, I really wonder if there’s an easy way to cool yourself whilst running in such humidity…

    Thanks for the tips 🙂

  21. Ethan, we feel your pain. Check us out. KryoSkinz Cooling Patches. We’ll help you beat the heat and Suffer Smarter.


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