Calculate heat index and wet bulb globe temperature for exercise safety.
Humidity impairs evaporative cooling, which is why the apparent temperature exceeds the air temperature. WBGT is preferred for exercise decisions because it includes solar radiation and wind, which the heat index ignores. Heat illness can develop rapidly and unacclimatised participants are at much higher risk, which is why guidance thresholds are set conservatively.
Heat Index / WBGT
Heat index is the Rothfusz regression on temperature and humidity; WBGT adds sun and wind
These figures are population-average estimates for training and recreational planning only and are not medical advice. Individual responses vary widely. Consult a qualified health professional before starting or significantly changing an exercise, supplement or nutrition programme, particularly if you have any medical condition. Heat illness is a medical emergency. If someone becomes confused, stops sweating, or collapses in the heat, call emergency services and begin cooling immediately. Follow the heat policy of your sport's governing body.
Heat index is the Rothfusz regression on temperature and humidity; WBGT adds sun and wind Humidity impairs evaporative cooling, which is why the apparent temperature exceeds the air temperature. WBGT is preferred for exercise decisions because it includes solar radiation and wind, which the heat index ignores.
Heat illness can develop rapidly and unacclimatised participants are at much higher risk, which is why guidance thresholds are set conservatively.
This calculator takes 4 inputs: Air temperature, Relative humidity, In direct sunlight, Wind speed. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.