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Wind Chill Calculator

Find how cold it feels on exposed skin from the air temperature and wind speed, using the official 2001 wind chill index of the US National Weather Service and Environment Canada, with frostbite times from the NWS chart.
  • Updated
  • Formula shown

Conditions

Sustained wind at the standard 10 m (33 ft) height, as in weather reports

Results

Wind chill (feels like)
−19.4°F
−28.6 °C · rounds to −19 °F
Frostbite on exposed skin
NWS chart cell: 0 °F, 15 mph (next colder and windier)
30 minutes or less
Colder than the air by
19.4°F
Air temperature
−17.8 °C
0 °F
Wind speed
24.1 km/h · 6.7 m/s
15 mph
Formula used
The 2001 wind chill temperature index
NWS (°F, mph)

Wind chill −19.4 °F (−28.6 °C) at 0 °F with 15 mph wind

Wind chill at 0 °F by wind speed
WindWind chillFrostbite (NWS chart)
5 mph−10.5 °FOutside the frostbite zones
10 mph−15.9 °FOutside the frostbite zones
15 mph−19.4 °F30 minutes or less
20 mph−22 °F30 minutes or less
25 mph−24.1 °F30 minutes or less
30 mph−25.9 °F30 minutes or less
40 mph−28.8 °F30 minutes or less
50 mph−31.1 °F30 minutes or less
60 mph−33.1 °F10 minutes or less

Frostbite risk: on the NWS chart, exposed skin can freeze in 30 minutes or less in these conditions. Cover your face, ears and hands, and watch for numb, white or grayish skin.

Wind chill describes heat loss from exposed skin. It assumes no sunshine and does not cool objects: a car or water pipe cannot get colder than the air temperature.

How to use the wind chill calculator

  1. Enter the air temperature and choose °F or °C. Negative values are fine.
  2. Enter the wind speed from a forecast or weather station in mph, km/h, m/s or knots. Forecast winds are measured at 10 m (33 ft), which the formula expects.
  3. Read the wind chill, the frostbite time for exposed skin and a table of wind chills at your temperature for other wind speeds.

The index is defined only for air at 50 °F (10 °C) or colder with wind of at least 3 mph (4.8 km/h); outside that range the calculator tells you so instead of giving a number.

Wind chill formula

°F and mph: WC = 35.74 + 0.6215T − 35.75V0.16 + 0.4275TV0.16
°C and km/h: WCI = 13.12 + 0.6215T − 11.37V0.16 + 0.3965TV0.16

T is the air temperature and V the wind speed at 10 m. Both lines are the same index, the Wind Chill Temperature introduced by the National Weather Service and Environment Canada in November 2001, written for different units: the first is the NWS form, the second the form Environment and Climate Change Canada publishes. It models heat loss from a human face walking at about 3 mph in the dark, and it was tested on volunteers in a chilled wind tunnel. The calculator uses the °C form when you enter °C and the °F form when you enter °F; the two agree to within a few hundredths of a degree.

Worked examples

  • 0 °F with a 15 mph wind: WC = 35.74 + 0 − 35.75 × 150.16 + 0 = −19.4 °F, which rounds to −19 °F, the NWS's own example. The chart puts this in the 30-minute frostbite zone.
  • −10 °C with a 20 km/h wind: WCI = 13.12 − 6.215 − 11.37 × 200.16 − 3.965 × 200.16 = −17.9 °C, so it feels like about −18 °C.

Wind chill chart (°F)

Computed with the calculator's engine; values match the NWS Wind Chill Chart. Marks show the chart's frostbite zones for exposed skin: † within 30 minutes, ‡ within 10 minutes, * within 5 minutes.

Wind (mph)40 °F30 °F20 °F10 °F0 °F−10 °F−20 °F−30 °F−40 °F
53625131−11−22 †−34 †−46 †−57 ‡
1034219−4−16−28 †−41 †−53 ‡−66 ‡
1532196−7−19 †−32 †−45 ‡−58 ‡−71 *
2030174−9−22 †−35 †−48 ‡−61 ‡−74 *
2529163−11−24 †−37 ‡−51 ‡−64 *−78 *
3028151−12−26 †−39 ‡−53 ‡−67 *−80 *
3528140−14−27 †−41 ‡−55 *−69 *−82 *
402713−1−15−29 †−43 ‡−57 *−71 *−84 *
452612−2−16−30 †−44 ‡−58 *−72 *−86 *
502612−3−17−31 †−45 ‡−60 *−74 *−88 *
552511−3−18 †−32 ‡−46 ‡−61 *−75 *−89 *
602510−4−19 †−33 ‡−48 *−62 *−76 *−91 *

Frostbite times on the NWS chart

The NWS chart shades three zones where exposed skin can freeze within 30, 10 and 5 minutes. This table lists, for each wind speed, the warmest air temperature in each zone. For conditions between rows and columns, the calculator uses the next colder temperature and the next higher wind speed, so it errs on the side of caution.

Wind (mph)30 minutes at or below10 minutes at or below5 minutes at or below
5−10 °F−40 °FColder than −45 °F
10−5 °F−25 °FColder than −45 °F
150 °F−20 °F−40 °F
200 °F−15 °F−35 °F
250 °F−10 °F−30 °F
305 °F−10 °F−25 °F
355 °F−5 °F−20 °F
405 °F−5 °F−20 °F
455 °F−5 °F−15 °F
505 °F−5 °F−15 °F
5510 °F0 °F−15 °F
6010 °F0 °F−10 °F

Wind chill chart (°C, km/h)

Wind (km/h)5 °C0 °C−5 °C−10 °C−15 °C−20 °C−25 °C−30 °C−35 °C−40 °C
103−3−9−15−21−27−33−39−45−51
201−5−12−18−24−30−37−43−49−56
300−6−13−20−26−33−39−46−52−59
40−1−7−14−21−27−34−41−48−54−61
50−1−8−15−22−29−35−42−49−56−63
60−2−9−16−23−30−36−43−50−57−64

What wind chill does and doesn't mean

  • It is about skin, not objects. Wind makes exposed skin lose heat faster, but a parked car, a water pipe or a thermometer cannot cool below the actual air temperature.
  • Sunshine helps. The index assumes a clear night sky; bright sun can make it feel noticeably milder.
  • Frostbite times are for exposed skin on typical adults. Children, older people and anyone wet, tired or with poor circulation can be affected sooner.
  • Hypothermia can occur at temperatures well above those on the frostbite chart, especially when wet. Dress in layers, cover your head and hands, and get indoors if you start shivering uncontrollably.

In hot weather, use the heat index calculator. The dew point calculator shows how much moisture is in the air.

Frequently asked questions

How is wind chill calculated?

The NWS formula is WC = 35.74 + 0.6215T − 35.75V^0.16 + 0.4275TV^0.16, with T in °F and V in mph. At 0 °F with a 15 mph wind it gives −19 °F. The metric version is WCI = 13.12 + 0.6215T − 11.37V^0.16 + 0.3965TV^0.16 with °C and km/h.

When does wind chill apply?

The index is defined only for air temperatures of 50 °F (10 °C) or colder and wind speeds of at least 3 mph (4.8 km/h). In warmer or calmer conditions the air temperature itself is the better guide.

How fast can frostbite happen?

On the NWS chart, exposed skin can freeze in 30 minutes once the wind chill reaches about −18 °F (−28 °C), for example 0 °F with a 15 mph wind. At −20 °F with a 15 mph wind it is 10 minutes, and at −40 °F with the same wind, 5 minutes.

What is the wind chill at −10 °C with a 20 km/h wind?

About −17.9 °C, which Environment Canada would report as −18. The wind makes exposed skin lose heat as fast as it would in calm air at about −18 °C.

Can wind chill freeze water pipes or a car engine?

No. Wind chill describes heat loss from skin. Wind makes objects cool down to the air temperature faster, but they cannot get colder than the air, so pipes only freeze if the air itself is below freezing.

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