Heat & humidity pace calculator.
Slows your goal pace for temperature and humidity using the same coefficients elite coaches apply: ~0.4%/°F above 60°F + 0.2%/% above 60% RH. Includes heat index and risk level.
Frequently asked
How much does heat slow my pace?
About 0.4% per °F above 60°F. At 85°F that's roughly 10% slower than ideal conditions for the same effort.
How does humidity affect performance?
Humidity reduces evaporative cooling. Pace slows ~0.2% per % humidity above 60%. Dew point above 65°F is where most runners feel a hard hit.
What's a dangerous heat index for running?
Above 90°F: caution. Above 103°F: dangerous. Above 125°F: extreme — do not run outdoors.
Should I always slow down in heat?
Yes. Holding pace in heat sharply raises core temperature and heat-illness risk. Run by effort or HR, fuel and hydrate more, and start earlier.
VDOT calculator
Jack Daniels race predictor and training paces — apply this heat adjustment on top of your goal pace.
Sweat & sodium loss calculator
Personal hourly sweat rate and sodium loss — essential when temperatures climb.
Dew point calculator
Dew point from temperature and humidity, mapped to a runner-specific comfort scale.
Train smart in the heat. Coach the rest.
Pace adjustment is step one. 1:1 coaching builds heat tolerance the right way — without breaking your block.
Boston-based · Trilingual EN/PT/ES · RRCA · USAT · TrainingPeaks L2 · 12× Boston qualifier