Heat pace calculator
How much to slow down when it’s hot: temperature and humidity in, dew point and an adjusted pace out.
Guideline based on the widely used temperature + dew point chart (combined score 147°F). It is a starting point, not a law — on hot days, effort and heart rate are more honest than any pace.
Heat does not mean lost fitness — an adjusted pace in July is the same effort as your normal pace in October. If you are not sure what your normal paces should be in the first place, the training pace calculator derives them from a race you’ve actually run.
Common questions
How much slower should I run in the heat?
It depends on the combination of temperature and dew point, not temperature alone. As a guideline: mild mugginess costs about 1%, a warm-humid day 3–6%, and a genuinely hot-humid day 8–10% or more — at which point pace targets stop being useful and effort should lead. This calculator applies that standard chart for you.
Why does dew point matter more than humidity?
Relative humidity changes with temperature; dew point measures the actual moisture in the air, which decides how well sweat evaporates — your main cooling system. Two 28°C days can feel completely different: dew point 12°C is pleasant, dew point 21°C is heavy. That is why the guideline uses temperature plus dew point.
Should I adjust my race pace in hot weather?
Yes — from the start, not after you blow up. Banking time early in a hot race is the classic mistake: overheating compounds, and the fade costs far more than the adjustment would have. Start at the adjusted pace and speed up late if you feel strong.
When should I ignore pace completely?
When the combined temperature + dew point score climbs past the top of the chart, or whenever heart rate is drifting well above normal for the effort. Run by feel, shorten if needed, and move quality sessions to cooler hours. Heat adaptation is real but takes about two weeks of regular exposure.
Related: easy pace checker · training pace calculator · free training plans
