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The calculator applies the official 2001 National Weather Service wind chill formula to your air temperature and wind speed. If you enter Celsius or km/h, your values are converted first: Fahrenheit equals Celsius × 9/5 + 32, and mph equals km/h divided by 1.609344. Wind speeds below 3 mph barely disturb the warm air layer on your skin, so the result simply equals the air temperature. Above 50 degrees Fahrenheit (10 degrees Celsius) the formula does not apply, because wind then cools you through evaporation and feels pleasant rather than colder. Every result shows the feels-like temperature in your chosen unit, how many degrees colder it feels than the actual air temperature, the estimated frostbite time for exposed skin, and the NWS danger level. These are planning estimates, not professional medical advice; always follow official weather warnings.
The US National Weather Service and Environment Canada adopted the current wind chill formula in 2001 after wind-tunnel trials measured how fast exposed facial skin cools at different temperature and wind combinations. The formula is: wind chill = 35.74 + 0.6215 × T - 35.75 × V⁰.16 + 0.4275 × T × V⁰.16, where T is the air temperature in Fahrenheit and V is the wind speed in miles per hour. It replaced the older 1945 Siple-Passel index, which timed how fast water froze in cans and overstated the cooling effect at high wind speeds; the 2001 revision typically reads 10 to 15 degrees warmer than the old formula on very windy days. Wind chill works because moving air strips away the thin warm boundary layer your skin heats around itself and replaces it with fresh cold air. The faster the wind, the faster your skin loses heat, even though the thermometer has not moved.
Enter the air temperature and choose Fahrenheit or Celsius. Enter the wind speed and choose mph or km/h; the calculator converts metric values automatically. Press Calculate to get the wind chill feels-like temperature in your chosen unit, how many degrees colder it feels than the actual air temperature, the estimated frostbite time for exposed skin, and the NWS danger level. If the wind is below 3 mph, the result equals the air temperature, because calm air barely disturbs the warm layer on your skin. If the air temperature is above 50 degrees Fahrenheit (10 degrees Celsius), the calculator will tell you wind chill does not apply instead of returning a misleading number.
The National Weather Service groups wind chill values into four danger bands. From 19 degrees Fahrenheit and up, conditions rate as Cool: dress warmly, with no significant frostbite risk. From -20 to 19 degrees, the rating is Cold with hypothermia risk, and exposed skin can develop frostbite in about 30 minutes. From -37 to -20 degrees, the rating is Very Cold with frostbite danger, and exposed skin can freeze in about 10 minutes. Below -37 degrees, the rating is Extreme Cold: stay indoors, because exposed skin can freeze in under 5 minutes. These bands assume exposed skin; proper clothing, dry conditions, and shorter exposure times reduce the real risk considerably.
Frostbite is the freezing of skin and the tissue beneath it, and early signs include numbness and pale or grayish skin. On the NWS scale, frostbite times for exposed skin are: over 30 minutes when wind chill is above -18 degrees Fahrenheit, about 30 minutes from -18 to -31 degrees, about 10 minutes from -32 to -47 degrees, and under 5 minutes at -48 degrees or colder. Hypothermia is a separate danger: core body temperature dropping below 95 degrees Fahrenheit, which can develop even above freezing if you are wet, exhausted, or badly dressed. The most effective protection is layering: a moisture-wicking base layer, an insulating mid-layer, and a wind-resistant outer shell, with your head, hands, ears, and feet covered. Wet clothing loses most of its insulating value, so staying dry matters as much as staying warm.
Wind chill describes heat loss from warm living skin, not the temperature of the air itself. A car engine, a water pipe, or a rock cools faster in wind, but wind alone can never push an object below the actual air temperature. Pipes freeze based on the thermometer reading, not the wind chill: water freezes when the air reaches 32 degrees Fahrenheit (0 degrees Celsius), regardless of wind speed. Confusing the two is the most common wind chill mistake. Related: sunshine can make exposed skin feel 10 to 18 degrees warmer than the reported wind chill, because the formula assumes nighttime conditions with no solar heating.
Wind chill and the heat index are the two ends of the feels-like temperature scale, and they use completely different formulas for opposite seasons. Wind chill combines air temperature with wind speed to show how cold winter air feels on exposed skin, and it only applies at 50 degrees Fahrenheit or below. The heat index combines air temperature with relative humidity to show how hot summer air feels, because humid air slows the evaporation of sweat; it only matters at about 80 degrees Fahrenheit and above. Try our heat index calculator when summer humidity makes the thermometer feel like an understatement.
Wind chill is calculated with the 2001 National Weather Service formula: 35.74 + 0.6215 × T - 35.75 × V to the power of 0.16 + 0.4275 × T × V to the power of 0.16, where T is the air temperature in Fahrenheit and V is the wind speed in miles per hour. Metric inputs are converted first. For example, 20 degrees Fahrenheit with a 15 mph wind gives a wind chill of about 6 degrees Fahrenheit, which feels almost 14 degrees colder than the air.
Wind chill becomes actively dangerous below about 0 degrees Fahrenheit. From 0 to -18 degrees, exposed skin can develop frostbite within 30 minutes. Below -28 degrees it can happen in 10 to 15 minutes, and below -50 degrees frostbite is possible in under 5 minutes. Hypothermia risk rises whenever wind chill stays below freezing during long exposure.
It depends on the wind chill value, not just the air temperature. Above -18 degrees Fahrenheit, the risk is low and frostbite takes over 30 minutes on exposed skin. From -18 to -31 degrees, expect about 30 minutes; from -32 to -47 degrees, about 10 minutes; at -48 degrees or colder, under 5 minutes. Covering skin and staying dry extends these times.
No. Wind chill only describes heat loss from warm living skin. Inanimate objects like pipes, car radiators, and buildings cool to the actual air temperature, never below it. A pipe freezes when the thermometer reads 32 degrees Fahrenheit or lower, no matter what the wind chill says.
Above about 50 degrees Fahrenheit (10 degrees Celsius), wind does not make your body feel meaningfully colder, so the National Weather Service does not calculate a wind chill value there. In milder weather, moving air helps sweat evaporate and usually feels pleasant. The formula was calibrated for cold conditions and gives unreliable results outside its valid range.
They are related ideas for opposite extremes. Wind chill shows how cold winter air feels by combining temperature with wind speed, using the NWS formula for temperatures at or below 50 degrees Fahrenheit. The heat index shows how hot summer air feels by combining temperature with humidity, using the Rothfusz regression for temperatures around 80 degrees Fahrenheit and above.
When the wind is calm or below 3 mph, the NWS formula is not considered reliable, so the wind chill is treated as equal to the air temperature. This calculator follows that practice: enter any wind speed under 3 mph and the result will match the air temperature you entered.
No. The wind chill, frostbite times, and danger levels on this page are planning estimates based on the National Weather Service scale, not professional medical advice. Frostbite risk varies with clothing, moisture, health, and individual factors. Follow official weather warnings, and seek medical help for signs of frostbite or hypothermia.
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