How to run in the heat: 12 ways to stay cool
Short answer: run when the sun is low, slow down by effort, wet your skin, drink to thirst with salt on runs over an hour, and allow two weeks to adapt. Stop at the first dizziness, confusion or chills.
Before you go #
- Check the dew point, not just the temperature. Under about 55°F is comfortable; over 70°F is oppressive. A warm, humid morning can cost 15–40 s/mile, a muggy one more. What drives the slowdown.
- Go early, or late if it's drier. Dawn is coolest but often most humid. Compare both.
- Choose shade. Sun adds heat the thermometer misses, so the same hour costs more in full sun than in shade or under cloud.
- Start cool. A cold drink or slushy, or a cold towel on your neck, buys you the first miles.
- Dress light. Light colors, thin fabric, a cap, sunglasses, sunscreen.
On the run #
- Run by effort, not pace. Hold an easy effort or heart rate and let the pace drop. Slower runners lose more per mile, not less.
- Wet your skin. Sweat cools only when it evaporates. Pour water on your head and neck; wear a wet buff or ice in your cap.
- Drink to thirst. Carry water past about 45 minutes.
- Take salt past an hour. Sports drink, salt tabs or salty food. Hours of plain water can dilute your blood sodium dangerously.
- Run loops. Water and an exit every few miles beat an exposed out-and-back.
Over the summer #
- Adapt for 10–14 days. Most of the gain comes in week one: you sweat sooner, your heart rate drops, runs feel easier. Keep those runs short and easy.
- Respect bad days. Illness, poor sleep, alcohol and some medications raise heat risk. Go shorter, earlier or indoors.
When to stop #
Dizziness, nausea, unusual weakness, or goosebumps and chills in the heat: stop, find shade, cool down. Confusion, slurred speech or collapse is heat stroke: call 911 and start cooling immediately. Warning signs in detail.
On race day #
Races fly a WBGT heat flag. Yellow: slow your goal. Red: run to finish, not for time. Black: races are usually cancelled. What each flag means.
Questions #
How long does it take to adapt to running in the heat?
10 to 14 days of running in heat, with most of the change in the first week.
Is it better to run in the morning or evening in summer?
Usually morning: the air is coolest and the sun is low. But dawn is often the most humid hour, so a dry evening can be better. Compare the dew point as well as the temperature.
How much water should I drink on a hot run?
Drink to thirst, carry water past about 45 minutes, and add salt past an hour. Drinking far more than you sweat is dangerous.
Is it safe to run in 90-degree heat?
Only short, slow and early, in shade, if you're adapted. Humidity and sun raise the risk fast. Stop at any dizziness, confusion or chills.
Sources #
Related guides
ArcPace scores every hour of your forecast 0–100, with the pace cost at your easy pace and what to wear. Free for iPhone. Get it on the App Store