Wind Chill Calculator
Enter the air temperature and wind speed to find the wind chill, the temperature it actually feels like on exposed skin. Switch freely between metric and imperial units. Along with the feels-like temperature you get the estimated time to frostbite, the danger category, and a full show-your-work panel using the official 2001 NWS/Environment Canada formula.
What is wind chill?
Wind chill (also called "feels-like" temperature or the apparent temperature) is a measure of how cold the air feels on exposed human skin when wind is blowing. Moving air strips away the thin layer of warm air that your skin produces, accelerating heat loss from your body. The faster the wind, the faster that insulating layer is replaced with cold air, and the colder you feel. Wind chill is not the temperature of the air itself - it describes the rate of heat loss from your skin. A thermometer placed outdoors is not affected by wind chill; only living things that generate heat are.
The 2001 NWS/Environment Canada formula
The formula used here is the joint NWS/Environment Canada standard adopted in November 2001 after the older Siple-Passel index was found to overstate cooling at high wind speeds and understate it at moderate speeds. The new formula is based on the heat transfer science of a human face, the body part most commonly exposed. The imperial version is: Wind Chill (F) = 35.74 + 0.6215 x T - 35.75 x V^0.16 + 0.4275 x T x V^0.16, where T is air temperature in degrees Fahrenheit and V is wind speed in miles per hour. The metric equivalent uses Celsius and km/h with slightly different constants. The formula is valid for temperatures at or below 50 F (10 C) and wind speeds of 3 mph (4.8 km/h) or greater.
How to use this calculator
Choose imperial (Fahrenheit and mph) or metric (Celsius and km/h), then enter the air temperature and the current or forecast wind speed. Your wind chill temperature, temperature drop, frostbite risk, and danger level update instantly. The "show your work" panel walks through every step of the calculation. The chart shows how the wind chill would change if the wind speed were different, holding your entered air temperature constant. The reference table gives the NWS danger categories and frostbite times for quick field reference.
Frostbite, hypothermia, and cold-weather safety
Frostbite occurs when skin and underlying tissue freeze. It can begin in as little as 5 minutes at extreme wind chill values below -37 F (-38 C). Early signs include numbness, pale or grayish skin, and a hard texture. Hypothermia is a separate but related danger: it occurs when core body temperature drops below 95 F (35 C) and can develop even at temperatures well above freezing if a person is wet, exhausted, or inadequately dressed. Wearing moisture-wicking base layers, an insulating mid-layer, and a wind-resistant outer shell reduces both risks. Covering exposed skin - especially the face, ears, hands, and feet - is the single most effective protection. Wet clothing loses most of its insulating value, so staying dry is as important as staying warm.
Wind Chill Danger Levels (NWS Guidelines)
| Wind Chill (F) | Danger Level | Frostbite Risk | Action |
|---|---|---|---|
| Above 19 | Low / Cool | Minimal | Dress warmly for comfort |
| 0 to 19 | Cold | 30 min to frostbite | Layer up, cover extremities |
| -17 to -1 | Very Cold | 10 min to frostbite | Minimize exposure, watch for symptoms |
| -37 to -18 | Extreme Cold | 5-10 min to frostbite | Avoid outdoor exposure |
| Below -37 | Dangerously Cold | Under 5 min to frostbite | Stay indoors; life-threatening |
Based on National Weather Service cold-weather advisories. Wind chill values in degrees Fahrenheit. Frostbite times apply to exposed skin.
Frequently asked questions
What is the difference between wind chill and actual temperature?
The actual (dry-bulb) air temperature is the temperature measured by a thermometer in still air. Wind chill is the equivalent temperature that would cause exposed human skin to lose heat at the same rate as it currently does in the wind. The two are equal when the wind is calm. As wind speed increases, wind chill drops below the air temperature because moving air removes body heat faster. An object that does not generate its own heat - a rock, a car - is not affected by wind chill; it will eventually cool to the actual air temperature, not the wind chill temperature.
Does wind chill affect how quickly water freezes?
No. Wind chill describes heat loss from warm objects. Water freezes when the air temperature drops to 32 F (0 C) or below, regardless of wind speed. Wind might slightly accelerate how quickly exposed water surfaces reach freezing point, but once the water and the air are the same temperature, the wind chill concept no longer applies.
How cold is too cold to be outdoors?
There is no universal threshold - it depends on how long you are outside, what you are wearing, how active you are, and your health. The NWS advises limiting outdoor exposure when the wind chill falls below -15 F (-26 C) because frostbite can occur in 10 minutes or less. When wind chill drops below -37 F (-38 C), exposed skin can freeze in 5 minutes or less and the risk of hypothermia rises sharply even for healthy, dressed adults.
Why does the formula need a minimum wind speed?
At wind speeds below about 3 mph (4.8 km/h), the air near your skin is barely disturbed. The NWS formula was derived from controlled experiments with minimum air movement; applying it at near-zero wind speeds would give unreliable results. At calm conditions, the wind chill is simply equal to the air temperature. This calculator applies a 3 mph floor to match NWS practice.
Is wind chill the same as the Heat Index (feels-like in summer)?
They are related concepts for opposite extremes. Wind chill represents how cold the air feels on exposed skin in winter, accounting for heat loss from wind. The Heat Index represents how hot the air feels in summer, accounting for the reduced cooling power of sweat when humidity is high. Both are "apparent temperature" measures, but they use completely different formulas and apply in opposite seasonal conditions.
Why does wind chill only apply to living things, not car engines or pipes?
Wind chill describes the rate of heat loss from warm surfaces (skin generates heat at roughly 37 C / 98.6 F). An object that generates no heat - a car radiator at ambient temperature, a water pipe - is not affected by wind chill in the same sense. Those objects simply lose or gain heat until they reach the surrounding air temperature. Wind can speed up that process, but once they match the air temperature, wind chill becomes irrelevant.