Every runner has had that moment where you step outside, take one breath, and instantly think, “Oh. This is going to be gross.”
That’s humidity and dew point doing their thing.
We tend to obsess over temperature because it’s the number we understand. But temperature alone doesn’t tell you why your easy run suddenly feels like a tempo workout or why your heart rate behaves like it has a personal vendetta against you. The real culprits are humidity and dew point, and once you understand how they work, pacing in summer becomes a whole lot easier.
Let’s break it down in a way that even a brand-new runner—or a 5th grader—could understand.
What Humidity Actually Means
Think of the air like a sponge.
Humidity tells you how full that sponge is.
If your weather app says humidity is 80 percent, the “air-sponge” is already holding 80 percent of the water it can carry. That means your sweat has nowhere to go. Instead of evaporating (which is how your body cools itself), it just sits there on your skin like a sticky film. And when your sweat can’t evaporate, you get hotter, faster. Your heart rate jumps. Your breathing gets heavier. Everything feels harder.
But humidity alone doesn’t tell the whole story.
What Dew Point Means (and Why It Matters Way More)
Dew point is the temperature at which the air-sponge becomes completely full and can’t hold one more drop.
This number tells you how the air actually feels on your skin, in your lungs, and during your run. A high dew point makes the air feel swampy, thick, and heavy—like you’re running with a warm towel wrapped around your face.
Here’s the simplest way to understand dew point:
Below 50°F: Dry and comfortable. You’re in the sweet spot.
50–60°F: Moist but manageable.
60–65°F: Sticky. Your body starts working harder.
65–70°F: Very uncomfortable. Expect a performance dip.
70°F+: Oppressive. Slow down, hydrate, and don’t be a hero.
If humidity is the vibe, dew point is the truth.
Why This Makes Running Feel So Much Harder
Your body cools itself by sweating. When your sweat evaporates, you cool down.
When it can’t evaporate—because the air is too wet—you overheat.
That’s when you feel:
Heavy legs
Sky-high heart rate
Choppy breathing
Nausea or dizziness
A sudden “why does this feel impossible?” sensation
None of this means you’re out of shape. It means your internal A/C unit is maxed out.
How to Train Smarter in Heat, Humidity, and High Dew Points
You can’t out-tough the weather, but you can absolutely outsmart it.
Pace by effort, not your watch
Your “easy pace” in March is not your “easy pace” in July. Effort > ego.
Slow down before your body forces you to
This isn’t a downgrade. It’s long-term strategy.
Hydrate like an athlete
High humidity hides how much you’re losing—not the other way around.
Run early or late
The sun is often the bigger bully than the humidity itself.
Give yourself time to acclimate
Two to three weeks of consistent exposure helps your physiology adjust.
A Helpful Next Read
Want to go even deeper into how weather affects your pacing?
Check out my related post: How to Adjust Your Running Pace for Heat and Humidity
(Already linked internally where needed.)
Work With Me
Summer running isn’t about proving toughness. It’s about learning your environment, adjusting your strategy, and letting your training work instead of fighting conditions you weren’t meant to conquer.
If you want help dialing in your pacing, hydration, fueling, and overall strategy so your summer miles don’t feel like punishment, I’d love to work with you.
Explore coaching options or grab my Fuel Like You Mean It guide—the summer performance cheat code every runner needs.