Running in the heat doesn’t have to feel miserable. With the right heat acclimation plan, your body can adapt surprisingly quickly, making summer training safer and more productive.
You haven’t lost fitness, and you’re not going crazy; summer running is just harder. Running in the heat and humidity feels slower and harder, even when your fitness hasn’t changed a bit.
Whether you’re preparing for a summer marathon, just getting through the summer for a Fall marathon or getting ready for a hot destination race, heat acclimation can improve both your performance and your confidence on race day.
In an episode of the Tread Lightly Running podcast, we chat through heat acclimation strategies and cooling techniques to make summer running a little less miserable.
Heat Acclimation for Runners
Heat acclimation is your body getting better at handling heat stress over time.
Sounds straightforward, right? It is, until some try to turn it into a year-round project.
Some runners spend the winter sitting in saunas after every workout or layering up in heat suits to stay heat adapted. But that’s usually more than you need.
The catch is that staying heat acclimated takes ongoing work, and that extra heat stress still adds to your overall training load. If you’re consistently asking your body to recover from hard workouts and extra heat exposure, something has to give.
Instead, think of heat acclimation as something you do with purpose. The first couple of weeks of summer training or the lead-up to a hot destination race are great times to focus on it.
Outside of those windows, there’s usually very little payoff.
And if you have the choice, running in the heat is generally more effective than sitting in a sauna.
Why? Because your body responds differently when you’re moving versus sitting still. You’re always practicing pacing, hydration, and fueling in the exact conditions you’ll be racing or training in.
There’s another benefit that’s easy to overlook: confidence.
Every hot run teaches your brain that heat isn’t automatically a threat.
You learn what normal discomfort feels like, how your body responds, and that you can handle it.
That mental adaptation is just as valuable as the physical one when the temperatures climb.
We go deep into the strategies, tools, tips and the science in this episode of Tread Lightly. Here you’ll find a quick summary, but for all the nitty gritty listen up.
How Long Does Heat Acclimation Take?
For most runners, heat acclimation takes about 10-14 days of consistent exposure.
That means the first few hot runs may feel rough, but that doesn’t mean you’re doing anything wrong. In fact, that’s exactly how the process usually starts.
The important word here is consistent.
If the weather is all over the place, like one day it’s 90 and the next it’s 65, your body isn’t getting the repeated exposure it needs to fully adapt.
It doesn’t mean acclimation won’t happen, just that it may take a little longer.
If your goal is to build heat tolerance but you’re dealing with inconsistent weather, consider doing some of your easy runs during the warmest part of the day. Easy is the key word.
This isn’t the time to chase paces or squeeze in hard workouts. Wear sunscreen, bring electrolytes, and give yourself permission to slow down.
How do you know it’s working?
You’ll probably notice that you start sweating earlier in your run, your heart rate isn’t climbing quite as quickly, your breathing feels more controlled, and you’re feeling a little less drained than you did during those first hot runs.
Will the heat ever feel easy? Probably not.
But after a couple of weeks, there’s a good chance it’ll feel a whole lot more manageable, and that’s exactly what you’re aiming for.
Pre- and Mid-run Cooling Techniques
The goal with pre- and mid-run cooling is to stay ahead of the heat, not try to undo it after you’re already overheating.
Think of cooling strategies as part of your race or training plan, just like hydration and fueling.
Checkout our list of which run cooling techniques (and gadgets like the Omius headband) actually work from real world testing.
Here are a few cooling strategies worth trying:
- Fill your water bottle halfway the night before and freeze it so you can top it off with water or electrolyte, which will help keep your drink cold as you run.
- Consider light, breathable long sleeve running sun shirts with UV protection, especially if it’s sunny and dry. It sounds counterintuitive, but keeping direct sun off your skin can feel cooler than bare skin, especially at altitude.
- Pre-cool by wearing an ice vest, or a DIY version with frozen water bottles tucked into a hydration pack, helps to lower your core temperature before you even begin.
- Hold something cold in your hand. Grabbing a cold water bottle or using something like the CryoPalm for at least a minute, especially during a rest interval, can help with perception of effort and short, high-intensity performance.
- Refuel after your run, even if you don’t feel like it. Your appetite often gets suppressed by the heat, but a combo of carbs and protein post-run supports your body’s heat adaptation. If nothing sounds appealing post-run, try some of these post-run meal ideas.
Signs and Symptoms of Heat Illness
Most of what you’re feeling on a hot run is probably…just summer running.
The heat makes every mile feel harder. Your heart rate climbs faster, your perceived effort goes up, and even an easy pace can suddenly feel like work.
That’s all normal.
The key is knowing the difference between normal hard and signs that your body needs more than a little grit.
Instead of focusing only on your legs, check in with your whole body. Feeling dizzy, confused, or unusually fatigued isn’t just part of pushing through a tough run. Those are signs to slow down, stop, and reassess.
Swollen hands or fingers can be another clue, especially if they’re paired with a headache after your run. That combination may point to a sodium imbalance, whether you’re getting too little or too much.
Not sure how much sodium you actually need? We’ve put together a guide to make it easy to estimate your needs based on your training and sweat rate.
One symptom should never be ignored: if you stop sweating and start getting chills, end your run immediately and seek medical care.
While you’re waiting for help, start cooling your body with cold towels or ice packs. They can help lower your body temperature, but they aren’t a replacement for medical treatment.
The goal isn’t to worry about every ache or symptom. It’s to learn what’s normal for your body in the heat.
If something feels noticeably different than your usual hard-but-manageable summer run, listen to it.
Catching a probable early is always easier than trying to recover after you’ve pushed through it.
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