Why heat slows your running pace (and what to do about it)
The weather app says 95°F. At 5 am.
Same as yesterday. Same as last week. Until October.
Here’s what’s actually happening, and what to do about it.
Why running in the heat feels so hard
If you’re running in high temperatures, the pacing math is real: for every 10 degrees above 70°F, you might slow down by 10–30 seconds per mile.
It’s because your body’s rerouting blood to your skin to cool you off.
It’s your own personal AC system, which is great for survival. Less great for speed.
how to make your runs bearable(ish)
Start at about 80% of what feels normal
Check in with yourself every 10 minutes
Know that your heart rate will spike. It’s doing all that cooling work.
How to mute your inner critic on hot runs
The heat messes with your head because your inner critic pipes up.
You know the voice. ‘This is stupid. Why am I so slow? I should stop.’
And you’re trying to shut it up. Here’s how.
The critic:“Why am I so slow? I should be able to handle this.”
The mute button: Your body’s doing double duty and working overtime. It’s cooling you down and moving you forward. Of course you’re slower.
The critic:“Everyone else looks fine.”
The mute button: So do you, probably. Heat hits everyone but some are just better at hiding it.
The critic:“I’m weak for backing off.”
The mute button: Weak is ending up in the ER because you couldn’t admit it was hot.
Your inner critic is still going to pop up, but at least now you know it lies.
How to stay hydrated when it’s hot
Sip every 15-20 minutes, don’t wait until you’re thirsty.
Wear a running vest. It’s not just for fluids…the pockets are great for holding ice packs for max cooling on the run.
Going longer than an hour? You’re also losing sodium, not just water. Add electrolytes because plain water won’t replace what you’re sweating out.
Check your pee. If it looks like apple juice afterward, it’s time to drink more water. Aim for pale lemonade.
When to stop: signs your hot run has crossed a line
Goosebumps or clammy skin and it’s 90 degrees out
Sweating so much it feels like you stepped out of the shower fully dressed
Flu-level fatigue that stops you mid-stride
Racing heartbeat but not in a “yay, fitness!” way
Feeling woozy and lightheaded
Dizziness when you stand up, and you didn’t even spin around first
Muscle cramps, nausea, or a headache
Feeling terrible? Step one: Water + shade. Step two: Call your doc if you don’t feel better in an hour.
Thanks, Mayo Clinic, for this list.
How long does it take to get used to running in the heat?
It takes about 1-2 weeks to adapt to the heat. By then, your heart rate settles, and you’ll start sweating smarter.
Most of these changes kick in during the first week and keep improving through week two.
Your body’s got this figured out — now you do too.
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