What is the wind chill?
Type the air temperature and the wind speed from the weather report. The wind chill calculator shows how cold it feels on exposed skin, in °F and °C.
- Wind chill (°F)
- 6.2
At 20 °F with a 15 mph wind, the wind chill is 6.2 °F (-14.3 °C).
- Wind chill (°C)
- -14.3
- Feels colder by (°F)
- 13.8
Wind chill (°F): 6.2. At 20 °F with a 15 mph wind, the wind chill is 6.2 °F (-14.3 °C).
How to calculate
Computes the wind chill temperature (how cold it feels on bare skin) from the air temperature and wind speed with the 2001 NWS and Environment Canada formula, in °F and °C.
Example with the default inputs (Air temperature 20 °F, Wind speed 15 mph): At 20 °F with a 15 mph wind, the wind chill is 6.2 °F (-14.3 °C).
Method: WCT = 35.74 + 0.6215T − 35.75V^0.16 + 0.4275T·V^0.16, with T in °F and V in mph, for T ≤ 50 °F and V above 3 mph (NWS and MSC, 2001).
- The wind speed is at the standard height of 10 m (33 ft), as weather reports give it; the formula reduces it to face height.
- Bare face skin, walking into the wind at about 3 mph, with no sun; the NWS notes that bright sunshine can make it feel 10 to 18 °F warmer.
- Defined only at 50 °F (10 °C) or colder and at winds above 3 mph (4.8 km/h).
Worked examples
Each example is checked against the calculator on every build.
- Air temperature 0 °F, Wind speed 15 mph gives Wind chill (°F) -19.397954, Wind chill (°C) -28.554419.Source: NWS Wind Chill Chart (2001): −19 °F at 0 °F and 15 mph
- Air temperature 20 °F, Wind speed 15 mph gives Wind chill (°F) 6.218885, Wind chill (°C) -14.322842, Feels colder by (°F) 13.781115.Source: NWS Wind Chill Chart (2001): 6 °F at 20 °F and 15 mph
- Air temperature -10 °F, Wind speed 30 mph gives Wind chill (°F) -39.44667.Source: NWS Wind Chill Chart (2001): −39 °F at −10 °F and 30 mph
- Air temperature -4 °F, Wind speed 18.64 mph gives Wind chill (°C) -32.536433.
How it works
T is the air temperature in °F and V the wind speed in mph (at 10 m):
- Wind chill (°F) = 35.74 + 0.6215 T − 35.75 V^0.16 + 0.4275 T V^0.16
- Wind chill (°C) = (wind chill in °F − 32) × 5 ÷ 9
- Feels colder by = T − wind chill, in °F
Temperatures in °C are converted exactly to °F (°F = °C × 9 ÷ 5 + 32), and wind speeds in km/h, m/s or knots exactly to mph (1 mph = 0.44704 m/s, 1 km/h = 1/3.6 m/s, 1 knot = 1,852/3,600 m/s). The metric formula Environment Canada uses is the same equation with rounded coefficients, so it can differ from this page by a few hundredths of a degree.
No answer. The formula is defined only for T at or below 50 °F and V above 3 mph. The calculator reads each value back as the exact decimal typed (the page stores the temperature in kelvin and the speed in m/s, and reads each back as the decimal with the fewest significant digits, in one of the box's units, that gives the same stored number; on a tie, the unit listed first in the box's unit menu wins), so 10 °C counts as exactly 50 °F (allowed) and 4.828032 km/h as exactly 3 mph (not above it). Above 50 °F it shows "Wind chill is defined only at 50 °F (10 °C) or colder."; at 3 mph or less, "Wind chill is defined only for winds above 3 mph (4.828032 km/h)."
Rounding. The wind chill and the difference show with 1 decimal, rounded half up, with a trailing zero left off. V^0.16 is not exact, so the results are floating-point values.
Assumptions
- The model is bare face skin, walking at about 3 mph into the wind, with no sun.
- The wind speed is at 10 m (33 ft), as reported.
- Temperatures from −100 °F to 120 °F and winds up to 250 mph are accepted; the answer needs 50 °F or colder and more than 3 mph.
Worked examples by hand
20 °F and 15 mph. 15^0.16 = 1.54232. WCT = 35.74 + 0.6215 × 20 − 35.75 × 1.54232 + 0.4275 × 20 × 1.54232 = 35.74 + 12.43 − 55.138 + 13.187 = 6.2 °F (−14.3 °C), 13.8 °F colder than the air. The NWS chart shows 6.
0 °F and 15 mph. WCT = 35.74 − 35.75 × 1.54232 = −19.4 °F (−28.6 °C). The NWS chart shows −19.
−10 °F and 30 mph. 30^0.16 = 1.72321. WCT = 35.74 − 6.215 − 61.605 − 7.367 = −39.4 °F. The NWS chart shows −39.
−20 °C and 30 km/h. −20 °C = −4 °F and 30 km/h = 18.641 mph. WCT = −26.6 °F = −32.5 °C. Environment Canada’s table shows −33.
Other questions people ask
What is wind chill?
Wind chill is how cold the air feels on bare skin when the wind blows. Wind carries heat away from the skin faster, so it feels colder than the thermometer reads. At 20 °F with a 15 mph wind, it feels like 6 °F.
How is wind chill calculated?
The US National Weather Service and Environment Canada have used the same formula since November 2001: WCT = 35.74 + 0.6215T − 35.75V^0.16 + 0.4275T·V^0.16, with T in °F and V the wind speed in mph. In metric it is 13.12 + 0.6215T − 11.37V^0.16 + 0.3965T·V^0.16, with T in °C and V in km/h.
When does wind chill apply?
The NWS defines wind chill only at air temperatures of 50 °F (10 °C) or colder and wind speeds above 3 mph (4.8 km/h). Outside those limits the calculator shows no answer; for hot weather, use the heat index.
When is wind chill dangerous?
The colder the wind chill, the sooner bare skin can freeze. The NWS wind chill chart shades the wind chills where frostbite can set in within 30, 10 and 5 minutes. When the wind chill is well below 0 °F, cover exposed skin and limit time outside.
Can wind chill freeze water or cool a car below the air temperature?
No. Wind chill describes heat loss from warm skin. An object that is not warmer than the air, like a pipe or a car, cools only to the air temperature, just faster in the wind.
Which wind speed should I use?
The speed from the weather report, which is measured at 10 m (33 ft) above the ground. The formula already adjusts it down to face height. Wind speeds in km/h, m/s or knots are converted exactly to mph.