Wind Chill Index Calculator
Find how cold it actually feels using the National Weather Service wind chill formula, plus a frostbite risk guide.
🥶 What is the Wind Chill Index?
The wind chill index is a measure of how much colder moving air makes exposed skin feel compared to the actual air temperature shown on a thermometer. Wind strips away the thin layer of warm air that naturally forms next to skin, speeding up heat loss and making cold weather feel far more dangerous than the raw temperature alone suggests.
Meteorologists issue wind chill warnings ahead of winter storms so outdoor workers, hikers, and commuters know how quickly frostbite can set in. Ski resorts post wind chill alongside temperature so visitors dress appropriately for exposed lift lines. Military and expedition planners use wind chill tables to set safe exposure time limits in extreme cold. Parents and school officials use it to decide whether outdoor recess or sports practice is safe.
A common misconception is that wind chill changes the actual temperature of objects, like a car engine or an exposed water pipe. It does not. Wind chill describes an accelerated rate of heat loss specific to living skin trying to maintain body temperature, an inanimate object cannot cool below the true air temperature no matter how hard the wind blows.
This calculator applies the official National Weather Service (NWS) 2001 wind chill formula, accepts temperature in Fahrenheit or Celsius and wind speed in mph or km/h, and pairs the result with a frostbite risk classification drawn from the NWS wind chill chart.
📐 Formula
📖 How to Use This Calculator
Steps
💡 Example Calculations
Example 1 — A Cold Winter Walk
T = 20°F, V = 15 mph
Example 2 — A Sharp Cold Snap
T = 0°F, V = 20 mph
Example 3 — Metric Units
T = −5°C, V = 30 km/h
❓ Frequently Asked Questions
🔗 Related Calculators
What is the formula for wind chill?
The NWS (2001) formula is WCI = 35.74 + 0.6215T - 35.75V^0.16 + 0.4275*T*V^0.16, where T is air temperature in degrees Fahrenheit and V is wind speed in miles per hour, measured at a standard height of 10 meters. It is valid for T at or below 50 degrees F and V at or above 3 mph.
Why does wind chill only apply to cold temperatures?
Wind chill models how fast exposed skin loses heat to moving cold air. Above roughly 50 degrees F (10 degrees C), the body is not losing heat fast enough for wind to meaningfully change how the air feels, so the NWS formula is not applied above that threshold.
What happens to wind chill below 3 mph?
Below 3 mph (4.8 km/h), the NWS formula reports wind chill as equal to the actual air temperature, since such light wind produces a negligible additional chilling effect on exposed skin.
How cold does it feel at 0 degrees F with 20 mph wind?
Using the NWS formula, 0 degrees F with a 20 mph wind produces a wind chill of about -22 degrees F, cold enough that the NWS wind chill chart places it in the zone where frostbite is possible on exposed skin within about 30 minutes.
At what wind chill does frostbite become a risk?
Per the NWS wind chill chart, frostbite risk on exposed skin rises noticeably once wind chill drops below about -18 to -19 degrees F (roughly -28 degrees C), with frostbite possible in about 30 minutes. Colder wind chills of -35 degrees F or below cut that time to about 10 minutes, and -60 degrees F or below to about 5 minutes.
Does wind chill affect car radiators or pipes the same way it affects skin?
No. Wind chill describes how fast living skin loses heat to moving air, not how cold an inanimate object's surface actually becomes. A car radiator or an exposed pipe will not cool below the actual air temperature no matter how strong the wind, unlike skin, which experiences an accelerated, physiologically real chilling effect.
Is wind chill the same as the heat index?
No, they are opposite-season counterparts. Wind chill estimates how much colder cold air feels due to wind-driven heat loss from skin, while the heat index estimates how much hotter warm air feels due to high humidity limiting the body's ability to cool itself by sweating.
Can this calculator use Celsius and km/h?
Yes. Switch the temperature unit to Celsius and the wind speed unit to km/h using the dropdown selectors, and the calculator converts the inputs internally before applying the NWS formula, then displays the wind chill in both units.
Who developed the current wind chill formula?
The National Weather Service, in cooperation with Environment Canada and outside experts, introduced the current wind chill formula in 2001 to replace an older 1945 formula, incorporating updated research on skin heat loss and using a wind speed measured at a more realistic face height.
Why does the formula use wind speed raised to the power 0.16?
The 0.16 exponent reflects how convective heat loss from skin scales with wind speed in the underlying heat transfer model the NWS formula is fit to, capturing the fact that wind chill drops quickly as wind speed first increases, then flattens out at higher wind speeds.