Use this wind chill calculator to estimate how cold it really feels outside. Enter the air temperature and wind speed, and the tool returns the wind chill temperature based on the official NWS wind chill formula. The result tells you the cooling effect of wind on exposed skin so you can plan for frostbite risk, hypothermia, and safe exposure time.
Calculate Wind Chill From Air Temperature and Wind Speed
The calculator needs two inputs:
- Air temperature: the reading on a thermometer, in °F or °C. The NWS formula is valid for temperatures at or below 50°F (10°C).
- Wind speed: measured in miles per hour (or km/h). The formula applies to wind speeds above 3 mph.
Enter both values, and the tool returns a feels-like temperature. That number tells you how cold a windy day feels on an adult human face.
How does the calculator work? It plugs your inputs into the National Weather Service windchill equation (covered below), then displays the apparent temperature. No guesswork, no rounding tricks.
A construction crew faces 20°F and 40 mph gusts. What is the feels-like temperature? The wind chill comes out near -10°F. At that level, frostbite can occur on exposed skin in about 30 minutes.
Can this calculator be used for indoor conditions? Not meaningfully. The wind chill formula was developed for outdoor conditions with natural wind. Indoor fans do not replicate the same kind of convection and heat transfer.
Wind Chill Temperature and How Your Body Loses Heat
Wind chill temperature describes how cold it feels when the speed of the wind combines with low temperatures to pull heat away from your body. It is not a separate measurement on a thermometer. It is an estimate of the rate of heat loss from exposed skin caused by wind.
Your body loses heat in several ways. The most relevant here is convection: moving air sweeps warm air away from your skin and replaces it with cold air. The faster the wind, the faster this exchange happens.
On a calm day at 10°F, your skin warms a thin layer of air right next to it. That layer acts like a small blanket. Wind strips that blanket away, so your skin temperature drops and your body loses heat much faster. That is why a windy day feels much colder than the actual air temperature.
Still air at 10°F already feels cold. Add 25 mph wind and the wind chill drops to about -11°F. The actual temperature has not changed, but the rate of heat loss from the body has increased sharply.
NWS Wind Chill Formula
The National Weather Service Windchill Equation
The official NWS wind chill formula used in the United States and Canada since 2001 is:
Wind Chill (°F) = 35.74 + 0.6215T − 35.75(V^0.16) + 0.4275T(V^0.16)
Where:
- T = actual air temperature in °F
- V = wind speed in miles per hour
What is the valid range? The formula works for temperatures at or below 50°F and wind speeds above 3 mph. Outside that range, the equation is not reliable.
Why did the NWS update the wind chill formula in 2001? The older formula (Siple and Passel, 1945) was based on experiments that measured how fast water froze in a plastic cylinder. It overestimated heat loss from human skin. The updated formula, developed by a team of researchers using human trial data and modern heat transfer modeling, gives results closer to what people actually experience. It assumes a walking speed of about 3 mph and uses face-height wind readings.
How is the wind chill formula calculated? You raise the wind speed to the 0.16 power, then apply the coefficients listed above. The calculator on this page handles all of that for you.
At an air temperature of 0°F, what wind speed produces a -25°F wind chill? Roughly 15 mph. Bump the wind to 30 mph and the wind chill drops closer to -33°F.
Wind Chill Temperature in Super Cold Weather
When temperatures drop well below zero, even moderate wind makes conditions dangerous. At -15°F with a 20 mph wind, the wind chill falls below -40°F. Exposed skin can freeze in under 10 minutes at those levels.
Super cold weather compounds problems:
- Batteries drain faster, making phones and emergency radios unreliable.
- Metal tools and equipment become hazardous to touch with bare hands.
- Vehicle engines may fail to start, leaving people stranded.
- Breathing very cold air can stress the lungs.
In extreme cold, layering warm clothes and covering all exposed skin is not optional. It is the primary line of defense. Outdoor work and winter sports need strict time limits when the wind chill drops below -25°F.
Is super cold weather so bad? Yes. At a wind chill of -40°F or lower, frostbite can occur in as little as 5 minutes. Hypothermia follows quickly if the body cannot maintain its core temperature.
When are Cold Weather Advisories or Extreme Cold Warnings issued? Thresholds vary by region, but a Wind Chill Advisory is common when the wind chill is expected to reach -20°F or colder. A Wind Chill Warning typically covers -35°F or below. At 0°F air temperature, a wind speed of about 40 mph is usually enough to trigger advisory criteria. Check your local weather office for exact thresholds.
Frostbite Risk on Exposed Skin
Frostbite happens when skin temperature drops low enough for tissue to freeze. Wind accelerates this process by increasing the rate of heat loss from exposed skin.
General frostbite timelines based on wind chill:
| Wind Chill | Approximate Time to Frostbite |
|---|---|
| -10°F to -24°F | 30 minutes |
| -25°F to -34°F | 15 minutes |
| -35°F to -49°F | 10 minutes |
| -50°F or lower | 5 minutes or less |
These are estimates for exposed skin on the face, fingers, and ears. Actual risk depends on moisture, clothing, circulation, and individual health.
At what wind chill does frostbite happen? Frostbite risk begins around 0°F wind chill for prolonged exposure. It becomes a serious concern below -10°F with shorter exposure time.
Is frostbite possible when the temperature is above freezing but the wind chill is below freezing? In theory, the wind chill formula can produce a below-freezing result even when the actual temperature is above 32°F. However, your skin is warmed by blood flow and will not freeze at those marginal levels. Frostbite in practice requires the actual air temperature to be well below freezing, combined with wind.
What does the wind chill read, and how quickly can frostbite develop? The calculator gives you the feels-like temperature. Use the table above to estimate how long you can safely stay outside with exposed skin at that wind chill.
Early signs of frostbite include numbness, white or grayish patches of skin, and a waxy texture. If you notice any of these during outdoor activities, get to a warm shelter immediately.
Hypothermia and Body Temperature
Hypothermia occurs when your internal body temperature drops below 95°F (35°C). Normal body temperature is about 98.6°F (37°C). A drop of just a few degrees can impair judgment, coordination, and eventually organ function.
Wind chill accelerates hypothermia because your body loses heat faster than it can produce it. Wet clothing, exhaustion, and dehydration make things worse.
Stages of hypothermia:
- Mild (90°F to 95°F / 32°C to 35°C): Shivering, clumsiness, difficulty thinking clearly.
- Moderate (82°F to 90°F / 28°C to 32°C): Shivering may stop. Confusion increases. Drowsiness sets in.
- Severe (body temperature below 82°F / 28°C): Loss of consciousness. Heart rhythm becomes irregular. This is life-threatening.
Severe hypothermia is a medical emergency. Call emergency services immediately.
Wind chill alone does not cause hypothermia. It is a combination of cold temperatures, wind, moisture, exposure time, and inadequate clothing. But a lower wind chill means your body loses heat faster, which shortens the window before hypothermia can set in.
Protect yourself:
- Wear layered warm clothes that wick moisture.
- Cover your head, neck, hands, and face.
- Limit exposure time in extreme cold.
- Stay dry. Wet clothing destroys insulation.
- Watch for signs in yourself and others during outdoor work or winter sports.
Wind Chill Calculator Estimates, Not Forecasts
This wind chill calculator provides estimates based on the NWS windchill equation. It is not a weather forecast and does not replace advice from the National Weather Service or a medical professional.
Key limitations to keep in mind:
- The formula assumes an adult human face at walking speed. Children, elderly individuals, and people with circulation issues may lose heat at different rates.
- It does not account for sunlight, humidity, or shelter. Direct sun can make conditions feel warmer than the calculated wind chill.
- Wind speed varies by location and elevation. A personal anemometer reading at face height gives the most accurate input. Official weather station winds may differ from what you experience on the ground.
- The formula is not designed for temperatures above 50°F or wind speeds at or below 3 mph.
Can wind chill be measured? Not directly. Wind chill is a calculated value, not something a thermometer reads. You measure air temperature and wind speed separately, then use the formula to estimate the cooling effect.
Use the result as a planning aid for outdoor activities, outdoor work, and cold-related safety decisions. For official warnings and local weather conditions, check your nearest NWS forecast office.