Wind Chill Calculator
Wind chill from air temperature and wind speed using the 2001 NWS formula, with frostbite times and an honest note about where the formula stops applying.
Wind Chill Calculator: with the default inputs, wind chill is -19.4 °F.
The dry-bulb air temperature from the thermometer or the forecast.
Sustained wind at 5 ft (1.5 m), which is what the 2001 formula uses — not the 10 m weather-station height.
What exposed skin loses heat as fast as.
- In both scales
- -19 °F (-29 °C)
- Degrees below the air temperature
- 19.4In Fahrenheit degrees. One Fahrenheit degree of difference is 0.56 Celsius degrees.
- Frostbite risk
- Frostbite possible on exposed skin in about 30 minutes.
- Frostbite in about
- 30Minutes on exposed skin, from the NWS wind chill chart. Blank when there is no chart-level risk.
- Formula applies?
- Yes — at or below 50 °F (10 °C) and above 3 mph (4.8 km/h).
Assumptions
- Uses the 2001 NWS / Environment Canada wind chill index, valid at or below 50 °F (10 °C) and above 3 mph (4.8 km/h).
- Wind speed is at 5 ft (face height); station wind reported at 10 m is roughly 1.5× that, and forecasts already correct for it.
- Assumes bare, dry skin with no sunshine. Direct sun can offset 10–18 °F; wet skin or clothing makes it worse.
- Frostbite times are the shaded bands of the NWS chart for healthy adults, not a medical prediction.
| Wind (mph) | Wind chill (°F) | Frostbite risk |
|---|---|---|
| 5 | -11 | Low |
| 10 | -16 | Low |
| 15 | -19 | 30 minutes |
| 20 | -22 | 30 minutes |
| 25 | -24 | 30 minutes |
| 30 | -26 | 30 minutes |
| 35 | -27 | 30 minutes |
| 40 | -29 | 30 minutes |
| 50 | -31 | 30 minutes |
| 60 | -33 | 10 minutes |
Frostbite bands are the shaded zones of the NWS wind chill chart: 30 minutes at −18 °F, 10 minutes at −33 °F, 5 minutes at −48 °F.
How this is worked out
The formula
2001 NWS / Environment Canada wind chill index (T in °F, V in mph): WC = 35.74 + 0.6215·T − 35.75·V^0.16 + 0.4275·T·V^0.16 Metric form (T in °C, V in km/h): WC = 13.12 + 0.6215·T − 11.37·V^0.16 + 0.3965·T·V^0.16 Valid for T ≤ 50 °F (10 °C) and V > 3 mph (4.8 km/h).
Open How it’s calculated above to see this worked through with your own numbers.
What you enter
- Air temperature
- The dry-bulb air temperature from the thermometer or the forecast.in °F, °C, K · from -80 to 60 · defaults to 0
- Wind speed
- Sustained wind at 5 ft (1.5 m), which is what the 2001 formula uses — not the 10 m weather-station height.in mph, km/h, m/s, kn · from 0 to 150 · defaults to 15
What you get back
- Wind chillmain answer
- What exposed skin loses heat as fast as.
- In both scales
- Degrees below the air temperature
- In Fahrenheit degrees. One Fahrenheit degree of difference is 0.56 Celsius degrees.
- Frostbite risk
- Frostbite in about
- Minutes on exposed skin, from the NWS wind chill chart. Blank when there is no chart-level risk.
- Formula applies?
What this assumes
- Uses the 2001 NWS / Environment Canada wind chill index, valid at or below 50 °F (10 °C) and above 3 mph (4.8 km/h).
- Wind speed is at 5 ft (face height); station wind reported at 10 m is roughly 1.5× that, and forecasts already correct for it.
- Assumes bare, dry skin with no sunshine. Direct sun can offset 10–18 °F; wet skin or clothing makes it worse.
- Frostbite times are the shaded bands of the NWS chart for healthy adults, not a medical prediction.
About this calculator
Wind chill is not a temperature. It is a heat-loss rate expressed as a temperature: the still-air temperature at which bare skin would lose heat as fast as it does at the actual temperature and wind speed. Your thermometer, your car and your pipes all experience the real air temperature — only exposed skin feels the wind chill.
The formula
The one used here is the 2001 index, adopted jointly by the US National Weather Service and the Meteorological Service of Canada, and it replaced the 1945 Siple–Passel formula that produced the famously exaggerated numbers older readers remember. The new model uses a modern heat-transfer model of a human face, wind measured at 5 feet (face height) rather than the 33-foot anemometer height, and a calm-skin resistance term. It is systematically warmer than the old one: −20 °F at 20 mph was "−67" under the old formula and is −48 under this one.
Where it stops applying
Two limits, both hard:
- At or below 50 °F (10 °C). Above that there is no wind chill index at all. Wind still cools you above 50 °F, but by evaporating sweat, which depends on humidity and is what the heat index handles.
- Above 3 mph (4.8 km/h). The NWS chart starts at 5 mph, and as the wind falls toward calm the regression stops behaving — at 1 mph and 20 °F it returns 21 °F, warmer than the air it is supposed to be chilling. Below the limit this calculator reports the plain air temperature and tells you it did.
The formula also assumes bare, dry skin at night with no sunshine. Direct sun can add the equivalent of 10–18 °F; wet skin or wet clothing takes far more away than the formula does.
Frostbite times
The bands come from the NWS wind chill chart: frostbite on exposed skin is possible in about 30 minutes at a wind chill of −18 °F, 10 minutes at −33 °F, and 5 minutes at −48 °F. Those are for healthy adults with dry, exposed skin. Children, older adults, anyone with poor circulation, and anyone wet or already cold reach the same damage faster.
Reading the results
The wind chill switches between °F, °C and K like any temperature on this site. Degrees below the air temperature is reported in Fahrenheit degrees, because a difference in Fahrenheit degrees is not the same size as a difference in Celsius degrees. If Formula applies? says no, the number shown is the plain air temperature.
Frequently asked questions
▸What is the wind chill at 0 °F with a 15 mph wind?
−19 °F. The 2001 NWS formula gives 35.74 + 0.6215×0 − 35.75×15^0.16 + 0 = −19.4 °F, which the NWS chart rounds to −19.
▸Is wind chill a real temperature?
No. It's the still-air temperature that would cool exposed skin at the same rate. Your car's engine block, a bucket of water and an outdoor thermostat all sit at the actual air temperature — wind chill only affects things warmer than the air, which is why it can't freeze pipes below freezing any faster than the air can.
▸Why did wind chill numbers get less extreme?
The 2001 formula replaced the 1945 Siple–Passel index, which was based on how fast water froze in plastic cylinders on an Antarctic expedition and badly overstated the effect. The new model uses a heat-transfer model of a human face and wind measured at face height.
▸At what wind chill does frostbite happen?
The NWS chart marks 30 minutes at −18 °F, 10 minutes at −33 °F and 5 minutes at −48 °F for exposed skin. Wet skin, wind on the face and existing cold injury all shorten those times considerably.
▸Does wind chill apply above 50 °F?
No. The index isn't defined above 50 °F (10 °C). Wind above that still feels cool by evaporating sweat, but that depends on humidity and is covered by the heat index rather than by wind chill.
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