A man runs towards the rising sun on a small road on the outskirts of Frankfurt, Germany, Tuesday, July 1, 2025.
(AP Photo/Michael Probst)
My high school cross-country coach used to tell me to go run when it’s blisteringly hot.
I said no.
But now I wish that I would have run in June and July.
Weather in your inbox
By signing up you agree to the Terms & Privacy Policy. Unsubscribe at any time.
Recent research reveals that running in hot, humid conditions offers a form of “poor man’s altitude training” that can dramatically improve your endurance performance.
Even though I was never going to be a running superstar, I could have definitely improved my PR if I had tried running in the hot and humid summer months.
.jpg)
Red blood cells moving through the body. These cells are responsible for many bodily functions including transferring oxygen to muscles and assisting with cooling.
(IANS)
How Your Body Handles The Heat
Let’s break down what happens when you first enter the oppressive heat and high humidity of the summer months.
Everyone knows that when you get hot, your body’s sweat glands ramp up water production as perspiration, helping to cool you off as it evaporates.
There is more going on than just sweating. The body accelerates its heart rate and increases blood flow to better move heat towards the surface.
That allows more heat to be dispersed from the body.
With blood focusing on cooling, this means that less blood – and therefore less oxygen – is available for the muscles used to kick, jump or throw.
But here’s where it gets interesting: your body is remarkably adaptable. Over four to five weeks of consistent heat training, remarkable changes begin to occur.
Your body begins focusing on increasing blood volume and red blood cell count, adaptations that mirror what happens during three weeks of high-altitude training.
And that can have a big impact on your performance.
When working out in peak summer months, your body prioritizes cooling and muscles get less blood during workouts. After about a month, your body increases blood volume to be able to better provide oxygen to muscles as well as cool the body effectively.
(For even more granular weather data tracking in your area, view your 15-minute details forecast in our Premium Pro experience.)
The Performance Payoff
So you have been suffering in the hot and humid weather. Now what? Was this all worth it?
Absolutely!
The increased blood volume and red blood cell count enhance your body’s ability to deliver oxygen to working muscles.
Many athletes also experience an improvement in VO2 max, the gold standard measurement of aerobic fitness that represents the maximum rate at which your body can use oxygen during exercise.
This boost in oxygen delivery capacity benefits athletes across a myriad of sports and exercises – whether you’re training for a triathlon, playing tennis or getting back into cycling.
When exercising outside in the hottest months, hydration is especially important. Consistency is key to increasing blood volume, and any heat related illness will hinder the ability to maximize results.
(Carlina Teteris/Getty Images)
Does This Torture Work Right Away?
Short answer? No.
You won’t necessarily feel like a superhero during those sweltering summer training sessions. However, you will start to get used to it as you continue to train. And the benefits will really start to be obvious as fall approaches.
Think about it: Training in triple digit heat indices will make temperatures in the 80s feel like a breeze (as long as you do it safely, of course!) It’s like making a withdrawal from the fitness bank account you’ve been contributing to all summer long.
(Further beef up your forecast with our detailed, hour-by-hour breakdown for the next 8 days – only available on our Premium Pro experience.)
Making Heat Training Work for You
If you’re intrigued by the potential of heat training, remember that adaptation takes time.
Those first few weeks will feel extra challenging as your body adjusts, so be patient with the process. Stay properly hydrated, listen to your body and consider adjusting your pace expectations during the hottest parts of summer.
So the next time you’re debating whether to brave the heat or hit the treadmill, consider stepping outside. Your future PR might depend on it.
Rob Shackelford received his undergraduate and master’s degrees from the University of Georgia, studying meteorology and experimenting with alternative hurricane forecasting tools.