Estimate apparent temperature from air temperature and wind speed using the NOAA/Environment Canada wind chill formula, with frostbite risk time and danger category.
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Feels like
-19.5°C
Actual: -10°C
Risk of frostbite. Dress in layers and cover exposed skin.
Wind chill (°C)
-19.5 °C
Wind chill (°F)
-3.1 °F
Wind speed (km/h)
30
Wind speed (mph)
18.6
Also in Physics
Science — Physics
Wind chill describes how cold the air feels on exposed skin due to the combined effects of low temperature and wind speed. The modern formula was developed by the US National Weather Service and Meteorological Service of Canada in 2001, replacing an older and less accurate index.
The 2001 NWS/MSC formula: WC = 13.12 + 0.6215T − 11.37V^0.16 + 0.3965TV^0.16, where T is air temperature in °C and V is wind speed in km/h. The formula is valid for temperatures at or below 10 °C and wind speeds of at least 4.8 km/h (3 mph).
The formula was derived from human trials and models the cooling of a human face walking into the wind. Wind chill does not lower the actual air temperature or freeze water faster than the actual temperature would.
The Canadian Wind Chill Warning Criteria define risk levels. At −27 °C wind chill, exposed skin can freeze in 30 minutes. At −35 °C, risk rises to 10 minutes. Below −48 °C, frostbite can occur in 5–10 minutes; below −55 °C in under 2 minutes.
Protective clothing, especially on the face, hands, and ears, dramatically reduces frostbite risk. Wet clothing or exposed skin significantly increases the rate of heat loss.
Frequently asked questions
At warmer temperatures, wind generally feels cooling and pleasant rather than dangerously cold. The physics of heat loss from skin at temperatures above 10 °C are better captured by the Heat Index or other comfort indices.
Wind chill only meaningfully applies to living organisms with internal heat sources. A car engine coolant, pipes, and inanimate objects cool to the actual air temperature, not the wind chill temperature. However, the rate at which they cool to that temperature is faster in wind.
Related
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