Heat & Humidity Calculator
Calculate how heat and humidity affect your running pace and race performance using research-based formulas. This calculator accounts for temperature, relative humidity or dew point, heat acclimatization status, and effort level to predict pace adjustments for hot weather conditions.
Units
Choose your preferred unit system for temperature and pace
Your Current Pace
Weather Conditions
Dew point is often more accurate for heat stress assessment
Heat Acclimatization Status
Heat acclimatization takes 10-14 days and significantly reduces performance impact. Full acclimatization can reduce heat impact by up to 65%.
Effort Level
Heat affects harder efforts more significantly than easy runs
⚠️ Important Safety Notice
These predictions are only an estimate. Heat adaptation and individual variation in heat tolerance play a major role in determining your body's response to heat. Train responsibly in hot conditions and consider rescheduling sessions during periods of extreme heat. Always listen to your body and stop if you experience dizziness, nausea, excessive fatigue, or confusion.
About Heat & Humidity Impact
Running in hot and humid conditions significantly impacts performance due to increased cardiovascular stress and impaired thermoregulation. This calculator uses research showing that optimal marathon temperature is around 10°C (50°F), with performance declining approximately 1.5-2% per 5°C above this temperature. Heat acclimatization through gradual exposure over 10-14 days can reduce performance impact by up to 65%.
Acclimatization Process: Adapt to heat through progressive exposure over 10-14 days. Benefits include increased plasma volume, earlier onset of sweating, reduced salt loss, and improved cardiovascular efficiency. Plan heat training if racing in hot conditions.
Dew Point vs. Humidity: Dew point is often more accurate for assessing heat stress as it represents absolute moisture in the air, while relative humidity varies with temperature. A dew point above 15°C (60°F) makes cooling difficult; above 20°C (68°F) is oppressive.
Tips for Hot Weather Running: Run early morning or evening, wear light colors, increase hydration before/during runs, reduce intensity, take walk breaks, watch for heat exhaustion signs (dizziness, nausea, confusion), and consider indoor alternatives in extreme heat.
Frequently Asked Questions
Found an error or have suggestions? Please email me at stefan@bflcoaching.com