Windchill converts the combined effect of cold and wind into an equivalent still-air temperature that has the same cooling power on exposed skin. Use it to judge frostbite risk on the face, ears, and hands for outdoor work and travel.
Conditions
Results
| Windchill (°C) | Frostbite risk on exposed skin |
|---|---|
| 0 to −27 | Low risk. Discomfort likely with prolonged exposure. |
| −28 to −39 | Frostbite possible in 10 to 30 min on exposed skin. |
| −40 to −47 | Frostbite in 5 to 10 min. Cover all exposed skin. |
| −48 to −54 | Frostbite in 2 to 5 min. Serious cold-weather gear essential. |
| ≤ −55 | Frostbite in under 2 min. Outdoor exposure highly dangerous. |
About this calculator
The 2001 wind chill formula is a joint standard between the US National Weather Service and Environment Canada, replacing the earlier 1945 Siple-Passel index. It is based on a physical model of heat transfer through the exposed cheek at a walking pace, calibrated against volunteer trials in cold chambers.
Formula. WCT = 13.12 + 0.6215 × Ta − 11.37 × V0.16 + 0.3965 × Ta × V0.16
Where WCT is the wind chill temperature in °C, Ta is the air temperature in °C, and V is the wind speed in km/h measured at the standard 10 m weather-station height.
Valid range. Ta at or below 10 °C, V at or above 4.8 km/h (1.3 m/s). Outside these ranges the calculator still shows a value but flags it, because the underlying physical model does not apply.
Frostbite time bands come from the same 2001 model, extended to predict skin cooling to the 4.8 °C freezing threshold on an exposed cheek. Bands assume bare skin and no acclimatisation. Well-fitted cold-weather clothing shifts the effective bands significantly warmer, but the face, ears, and any bare fingers remain the limiting sites.
Standard. NWS/Environment Canada joint operational standard, adopted November 2001. See Environment Canada, Wind Chill Definition.
Citation. Osczevski R, Bluestein M. The new wind chill equivalent temperature chart. Bulletin of the American Meteorological Society 86(10):1453–1458 (2005).