Wind chill calculator
How cold it feels on exposed skin when wind is added to the air temperature, with the Wind Chill Temperature index the US National Weather Service introduced on 1 November 2001, and Environment and Climate Change Canada's frostbite risk for the result.
Wind chill (example)
−26.0 °C · −14.8 °F
Moderate risk
Environment Canada: Frostbite risk if outdoors for long periods without adequate protection.
For −15.0 °C (5.0 °F) with a 30 km/h (19 mph) wind.
Frostbite risk by wind chill (Environment Canada)
| Wind chill | Risk | What Environment Canada says |
|---|---|---|
| −55 °C or colder | Extreme | DANGER! Outdoor conditions are hazardous: exposed skin can freeze in less than 2 minutes. |
| −48 to −54 °C | Severe | Severe risk of frostbite: exposed skin can freeze in 2 to 5 minutes. |
| −40 to −47 °C | Very high | Very high risk of frostbite: any exposed skin can freeze in 5 to 10 minutes. |
| −28 to −39 °C | High | High risk of frostnip or frostbite: any exposed skin can freeze in 10 to 30 minutes. |
| −10 to −27 °C | Moderate | Frostbite risk if outdoors for long periods without adequate protection. |
| 0 to −9 °C | Low | Slight increase in physical discomfort. |
Environment Canada reports wind chill when the temperature is 0 °C or below and the wind is 5 km/h or more, in whole degrees. The NWS publishes its own chart with frostbite times; its example: 0 °F with a 15 mph wind gives a wind chill of −19 °F, at which exposed skin can freeze in 30 minutes.
How it is calculated
The NWS formula, with T the air temperature in °F and V the wind speed in mph:
Wind chill (°F) = 35.74 + 0.6215·T − 35.75·V^0.16 + 0.4275·T·V^0.16
It is only defined for temperatures at or below 50 °F and wind speeds above 3 mph. For °C and km/h this calculator converts to °F and mph, applies the same formula and converts back, so both units always agree. The wind speed is the one in a weather report, measured 10 metres up; the NWS formula adjusts it to the height of a face, about 1.5 metres.
Worked example: 0 °F with a 15 mph wind (the NWS example)
15^0.16 = 1.5423 Wind chill = 35.74 + 0.6215 × 0 − 35.75 × 1.5423 + 0.4275 × 0 × 1.5423 = -19.4 °F ≈ -19 °F (-28.6 °C)
Reference table: wind chill in °C
| Air temperature | 10 km/h | 20 km/h | 30 km/h | 40 km/h | 60 km/h |
|---|---|---|---|---|---|
| 0.0 °C | -3 | -5 | -6 | -7 | -9 |
| −10.0 °C | -15 | -18 | -19 | -21 | -23 |
| −20.0 °C | -27 | -30 | -33 | -34 | -36 |
| −30.0 °C | -39 | -43 | -46 | -47 | -50 |
| −40.0 °C | -51 | -56 | -59 | -61 | -64 |
This calculator gives an estimate for learning and planning. It is not a forecast or a warning, and it cannot say whether conditions are safe. For decisions, follow your national weather service and local authorities.
Sources
- National Weather Service: Wind Chill Chart: the formula, where it is defined, and the 0 °F / 15 mph example
- National Weather Service Alaska Region: Wind Chill Temperature Index (brochure): introduced 1 November 2001; the NWS wind chill chart used in the tests
- Environment and Climate Change Canada: Wind chill and the Wind Chill Index: risk categories and how fast exposed skin can freeze
Questions
What is wind chill?
Wind chill is how cold it feels on exposed skin when wind is added to the air temperature, because wind carries body heat away faster. This page uses the Wind Chill Temperature index the US National Weather Service introduced on 1 November 2001, which is based on heat lost from human skin.
How fast can frostbite happen?
Environment and Climate Change Canada says exposed skin can freeze in 10 to 30 minutes at a wind chill of -28 to -39 °C, in 5 to 10 minutes at -40 to -47 °C, in 2 to 5 minutes at -48 to -54 °C, and in under 2 minutes at -55 °C or colder. The NWS gives the example of 0 °F with a 15 mph wind: a wind chill of -19 °F, at which exposed skin can freeze in 30 minutes.