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Wind chill (US NWS 2001 formula)

Computes the wind chill temperature using the US National Weather Service's 2001 formula.

Published for review. The Founder is checking every card himself; anything he strikes comes down the same hour.

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Inputs

temp_f (number, degrees F, required) max 50 : Air temperature.
wind_mph (number, mph, required) min 3 : Sustained wind speed.

Outputs

wind_chill_f (degrees F): Wind chill temperature.

Steps

NWS 2001 wind chill formula: WC = 35.74 + 0.6215*T - 35.75*V^0.16 + 0.4275*T*V^0.16, where T is air temperature in F and V is wind speed in mph.
Valid range: temperature at or below 50 F and wind speed at or above 3 mph. Outside this range the formula is not meaningful.
Round to the nearest whole degree.

Constants

wind_chill_valid_max_temp_f = 50 degrees F (source)
wind_chill_valid_min_wind_mph = 3 mph (source)

Sources

Wind Chill Chart and the 2001 NWS wind chill formula (National Weather Service (NOAA), 2026-09-30T19:52:00Z) - Official NWS wind chill formula adopted in 2001, valid for T<=50F and V>=3mph.

Worked example and test vectors

Name	Inputs	Answer
worked example	`{"temp_f":5,"wind_mph":25}`	-17 degrees F
test vector: milder cold	`{"temp_f":30,"wind_mph":10}`	21 degrees F

Published card

Address: 104e411069dd039c5ce057973264d2b4
Made at: 2026-09-30T22:39:30.722Z
Method sha256: a6f47736bb6ac3eeab0ba208400dfc8003a23756c464cc4d540df6af330f7b47

Download wind-chill-us-nws.card.json Download wind-chill-us-nws.cjs