Run early morning or near sunset — avoid 10 a.m.–4 p.m. peak heat. Wear light, breathable fabrics and a cap; sunscreen on exposed skin. When to skip: Do not run outdoors in heat advisories, extreme humidity with high heart rate, or if you feel faint or headachey before you start.

Heat & humidity

Hot and humid days

If you head out

Run early morning or near sunset — avoid 10 a.m.–4 p.m. peak heat.
Wear light, breathable fabrics and a cap; sunscreen on exposed skin.
Slow your pace 30–90 sec/mile — heat stress matters more than the watch.
Pre-hydrate and bring water on anything over 30 minutes.

Indoor alternatives

Treadmill in air conditioning — same time on feet, easier pace.
Pool walk or easy swim for cardio without overheating.
Indoor walking laps at a mall or gym track.
Swap to a rest day if you felt dizzy or nauseous on a recent hot run.

Do not run outdoors in heat advisories, extreme humidity with high heart rate, or if you feel faint or headachey before you start.

LetsRunNow provides general fitness education, not medical advice. Talk to your doctor before starting or changing an exercise program — especially if you have a health condition, are pregnant, are recovering from injury or illness, or have not been active recently. Extreme heat, cold, or poor air quality carry real health risks — when in doubt, move your run indoors. Read our full terms.

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