Enter today's temperature and dew point to get your exact heat-adjusted pace, so you stop judging summer runs against spring fitness and stop blowing up in hot races.
The formula combines air temperature and dew point, because dew point (unlike humidity %) tells you whether your sweat can actually evaporate and cool you.
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| Scenario | Conditions | Adjusted Pace | Finish Impact |
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Individuals respond to heat differently; treat results as a starting point.
Your body cools itself by evaporating sweat. When the dew point climbs, the air is already holding so much moisture that sweat sits on your skin instead of evaporating, and your core temperature rises. Your body responds by sending more blood to your skin for cooling, which leaves less oxygen-carrying blood for your working muscles. Same effort, slower pace.
That's why this calculator asks for dew point instead of "humidity %": relative humidity swings with air temperature, while dew point directly measures the moisture that determines whether your sweat can do its job.
Want the full chart and the physiology behind it? Read our guide to adjusting your pace in hot and humid weather.
Every weather app lists it. Here's where to look:
Apple Weather, Google, Weather.com, anything works. Search your run location, not your home, if they differ.
Dew point is usually listed near humidity, wind, and UV index. Use the hour you'll actually be running.
Air temp + dew point at your start time. That's everything the formula needs.
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Once air temperature plus dew point exceeds 130 combined, pace starts to suffer, and the penalty grows about 1% for every 10 points above that. A 75°F morning with a 60°F dew point (135) already calls for a small adjustment on hard efforts.
It scales with conditions: a mild summer morning might cost 5–10 seconds per mile, while a hot, humid afternoon can cost 30+ seconds per mile. The calculator above gives you the number for your exact conditions and pace.
On easy days, effort beats math: run at a conversational effort and let pace land where it lands. Use the calculated adjustment for workouts and races, where starting at the wrong pace has a real cost.
Relative humidity changes with air temperature; 90% humidity at 55°F is pleasant while 60% at 85°F is brutal. Dew point measures the actual moisture in the air, which is what determines whether your sweat can evaporate and cool you.
Yes, and race day is where they matter most. Starting a hot race at your cool-weather goal pace is the classic blow-up: you bank a small "cushion" in the first half and lose several times that in the second. Set your target with the adjusted pace, and if conditions improve late in the race, speed up then.
The calculator tells you how much to slow down. These guides show you how to need less of an adjustment:
