Wind Chill Calculator
With air temperature 20 °F, wind speed 20 mph, wind chill comes to 4.2 °F — feels like. It is reached in 6 steps, the last of which is applies ? wind_chill : temperature, and each one is printed on the page with its numbers filled in. The formula is the one published by NOAA National Weather Service, not an approximation fitted to it.
What the cold feels like once wind is taken into account, by the National Weather Service formula, with the frostbite time it implies.
Formula and sources checked · How we check
Air temperature 20 °F, Wind speed 20 mph
4.2 °F
Feels like for the example below. Editing a field recomputes the calculator below; this figure holds the answer the page was loaded with.
It is written into the HTML rather than drawn by a script, so a search engine reading this page without running JavaScript still finds an answer.
- Wind chill
35.74 + 0.6215 * 20 - 35.75 * 1.6149713 + 0.4275 * 20 * 1.61497134.243 °F- Inside the formula’s valid range
1- Reported wind chill
4.243 °F- How much the wind takes off
20 - 4.242781615.757 °F- Wind chill in Celsius
(4.2427816 - 32) * 5 / 9-15.421 °C- Frostbite on exposed skin in about
0 minutes
Worked example
20 °F with a 20 mph wind feels like 4 °F — sixteen degrees of difference, and the point at which exposed skin starts to matter on a long walk.
How to work it out yourself
- 1.Use the air temperature in the shade and the sustained wind speed, not the gusts.
- 2.Below 3 mph of wind there is no wind chill to report: the formula is undefined there and the answer is the air temperature.
- 3.Remember what it describes — heat loss from bare skin. It does not make water freeze faster, and a car left out overnight cools to the air temperature, not to the wind chill.
What wind does at 20 °F
| Wind speed (mph) | Feels like | How much the wind takes off |
|---|---|---|
| 5 | 13.0 °F | 7.02 °F |
| 10 | 8.9 °F | 11.15 °F |
| 15 | 6.2 °F | 13.78 °F |
| 20 | 4.2 °F | 15.76 °F |
| 25 | 2.6 °F | 17.35 °F |
| 30 | 1.3 °F | 18.7 °F |
| 35 | 0.1 °F | 19.87 °F |
| 40 | -0.9 °F | 20.91 °F |
| 45 | -1.8 °F | 21.84 °F |
| 50 | -2.7 °F | 22.69 °F |
Air temperature held at 20 °F.
The formula
- Wind chill
35.74 + 0.6215 * 20 - 35.75 * 1.6149713 + 0.4275 * 20 * 1.6149713 - Inside the formula’s valid range
- Reported wind chill
- How much the wind takes off
20 - 4.2427816 - Wind chill in Celsius
(4.2427816 - 32) * 5 / 9 - Frostbite on exposed skin in about
Source: NOAA National Weather Service — wind chill chart and formula
Questions people actually ask
- Does wind chill make things freeze faster?
- It makes them reach the air temperature faster, and no colder. Wind chill describes heat loss from a warm object — skin, mostly — so a pipe or a puddle already at the air temperature is unaffected. A car radiator will not freeze at a wind chill above the freezing point.
- Why did the formula change in 2001?
- The old 1945 figure came from measuring how fast water froze in a plastic cylinder on a roof in Antarctica, and it overstated the chill badly. The current formula is fitted to a model of heat loss from a human face, uses wind speed at five feet rather than at the 33-foot anemometer height, and assumes calm skin temperature — which is why modern wind chills look milder than the ones people remember.
- When does frostbite become a risk?
- The National Weather Service publishes thresholds: about 30 minutes to frostbite on exposed skin at a wind chill of −18 °F, 10 minutes at −28 °F, and 5 minutes at −40 °F. Those are for bare skin; covered skin has far longer, and wet skin far less.
- Is there a wind chill above 50 °F?
- Not a defined one. The formula is only valid at or below 50 °F with wind over 3 mph, and outside that range the weather services report the air temperature. In hot weather the equivalent concept is the heat index, which runs the other way.
Related
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- Dew Point CalculatorDew point from temperature and humidity by the Magnus formula, with what that dew point actually feels like.
- Fraction to Decimal CalculatorConverts fractions to decimals and back, to the nearest 16th, 32nd and 64th, with the millimeter equivalent.
- Military Time ConverterA clock time as military time, with the full chart of all twenty-four hours and the two readings people get wrong: midnight and noon.
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