Running in hot weather can make you wish for crisp, cool fall days.
But how do you stick to your running routine when the weather feels like a sauna? Is it safe to run in hot weather?
The good news is you don’t have to hit pause on your running until fall to make the most of running in hot weather.
But you will have to adjust your running when the temperature soars, and today we’ll answer some common questions about running in hot weather and the tips you need to know to stay cool on the run.
Let’s get started.
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LET’S ANSWER SOME COMMON QUESTIONS ABOUT RUNNING IN HOT WEATHER
Check the heat index before running in hot weather
Before running in hot weather, you’ll want to check the temperature *and* the heat index.
The heat index is the temperature and relative humidity that tells you what it really feels like outside. 1
So though it may be 80 degrees outside, the heat index will tell you that it will feel more like 88 degrees F because humidity makes it feel warmer and more uncomfortable.
How does humidity affect running?
Running in humid weather will seem hotter and more stifling because the air holds more water and prevents sweat from evaporating quickly to cool you off.
By contrast, running in hot, dry weather will help you stay cooler because sweat evaporates quickly because there’s less moisture in the air.
How much does heat affect running pace?
If you’ve ever tried running in 90-degree weather or running in 100-degree weather, you probably already know that it’s almost impossible to run at your usual pace.
But how much does heat affect running pace?
On scorching days, your body uses some of the energy typically reserved for maintaining your regular pace towards keeping you cool.
As a result, this diversion of energy slows your running speed by about 30 to 90 seconds. But, you may slow by more than 90 seconds, depending on how well you can handle running in hot weather.
So what temperature is too hot to run?
Running in 80-degree weather – Use caution because you may feel exhausted with prolonged exposure to running in hot weather.
Running in 90-degree weather – Use extreme caution because running for too long in 90-degree weather can lead to heat stroke, heat cramps, or heat exhaustion.
Running in 100-degree weather – Use extreme caution if you’re running because running in 100-degree weather can lead to heat stroke, heat cramps, or heat exhaustion.
This chart from the National Weather Service can help you decide.
But note, these heat index values are for shady areas, not areas exposed to direct sunlight. If you’re in direct sunlight, the heat index value can increase by up to 15 degrees F.
Here’s a heat index infographic to help you decide when it’s too hot to run.
HOW TO ADJUST TO RUNNING IN HEAT
Running in hot weather means you will need to make a few adjustments to your running routine to avoid overheating on your runs.
So here you’ll find a few tips on how to adjust to running in the heat.
Split your runs into two
There are some dangers of running in the heat such as sunburn, dehydration, and heat stroke, and the next best thing (if you want to avoid a treadmill run) may be to split your run into two.
If you’re training for a half marathon or a marathon, a long continuous run may not be your best option in soaring temps, but to help you tack on more mileage, consider splitting your run into two—one in the morning and the other in the evening.
Use walk breaks
Walking will help you maintain your running fitness because you’ll build time on your feet without excessive stress from the heat. For example, you could run for 2 minutes and walk for 1 minute or run until you feel like you need to cool down with a walk.
Run by feel instead of pace
Remember, running in hot weather means your body uses some of the energy typically reserved for maintaining your regular pace towards keeping you cool.
As a result, your running speed will slow anywhere from 30 to 90 seconds.
Maintaining your usual pace on a hot day can put excessive stress on your system and increase the risk of heat exhaustion.
But you can prevent yourself from overdoing it if you run by feel instead of pace using Rate of Perceived Exertion (RPE).
Rate of perceived exertion 2 is a way to measure physical activity intensity, or how hard you feel like you’re running.
For reference, an RPE of 1 is a gentle stroll and an RPE of 10 is a max sprint.
Running by RPE is a subjective measure, but on hot days running by RPE has several advantages over relying on your running watch:
- It encourages you to tune in and listen to your body’s signals.
- You can prevent overheating and heat exhaustion by tuning into your body.
- And, you can strike a balance between pushing yourself and avoiding excessive strain. This flexibility allows you to adjust your pace and effort based on the conditions and how your body responds to the heat.
Pre-cool yourself with a cooling vest
Wearing a cooling vest (like this cooling vest) a few minutes before your long run can lower your initial core temperature and it can make you feel more comfortable about doing a run in hot weather.
That’s because your body and mind limit how much heat you can tolerate on a hot day.
Physically, that limit is around 104 degrees, depending on your fitness level. After this point, your pace will likely plummet to a crawl.
But you can extend the time it takes for your core temperature to reach your upper limits of heat tolerance with a cooling vest.
Wear sunscreen to keep you cool
Wearing sunscreen can help you avoid both sunburn (which prevents you from cooling off) and dehydration. 3
The best way to avoid sunburn and skin damage is with sunscreen, 4
- Use sunscreen with a sun protection factor (SPF) of 30 or higher when you’re running outdoors, regardless of your skin color.
- About 15 to 30 minutes before your run, apply about 1 teaspoon of sunscreen to your face and neck and 1 ounce (about a shot glass full) for any exposed skin. Then, wait about 10 to 20 minutes before putting on your shorts and shirt.
- Reapply sunscreen every 2 hours
Find a shady trail
Running in hot weather means you’ll have the sun shining from above you and the heat radiating off the road.
Keep yourself cool by staying out of direct sunlight under a shady trail. If you’re looking for a trail, you’ll find a few running trail resources in this post.
Drink cool (not cold) fluids when you’re running in hot weather
It’s normal to want to reach for an ice-cold drink anytime you’re under the sun.
But when you’re running in hot weather, you’ll want to turn to cool fluids instead of icy cold ones because ice-cold drinks can cause stomach cramps.
You will need to keep your drinks cool (but not cold) throughout your run, especially if your long run is several hours long.
You could stash a few cold water bottles along your route, or freeze half the fluids in your water bottle or hydration pack before filling it to the top.
Remember to sip your fluids often, even if you don’t feel thirsty. And it might be a good idea to bring a recovery drink to help you recover after a run.
Know the symptoms of heat exhaustion
Quitting isn’t always a bad thing; it may be a very good thing when you’re showing early signs of heat exhaustion.
If you feel any of these symptoms, stop your run immediately, go to a cool place, and drink cool fluids. 5
- Cool, moist skin with goosebumps in the heat
- Heavy sweating
- Faintness
- Dizziness
- Fatigue
- Weak, rapid pulse
- Low blood pressure when standing
- Muscle cramps
- Nausea
- Headache
If you don’t feel better in an hour, contact your doctor.
We’ve talked about how to run in hot weather, but what should you do after a run in the heat? That’s where this free download can help.
Grab this download, and you’ll get a timeline of what to do after a run and what to drink to rehydrate after a run in the sweltering heat.
Sources
APA SIEGEL, RODNEY1; MATÉ, JOSEPH1; BREARLEY, MATT B.2; WATSON, GREIG1; NOSAKA, KAZUNORI1; LAURSEN, PAUL B.1 Ice Slurry Ingestion Increases Core Temperature Capacity and Running Time in the Heat, Medicine & Science in Sports & Exercise: April 2010 – Volume 42 – Issue 4 – p 717-725
doi: 10.1249/MSS.0b013e3181bf257a
Sigurbjörn Á. Arngrïmsson, Darby S. Petitt, Matthew G. Stueck, Dennis K. Jorgensen, and Kirk J. Cureton. Cooling vest worn during active warm-up improves 5-km run performance in the heat
Wallace, Phillip & McKinlay, Brandon & Coletta, Nico & Vlaar, Janae & Taber, Michael & Wilson, Philip & Cheung, Stephen. (2016). Effects of Motivational Self-Talk on Endurance and Cognitive Performance in the Heat. Medicine & Science in Sports & Exercise. MSSE-D-16-00733R2. 10.1249/MSS.0000000000001087.