What Is Wind Chill?
Wind chill describes how cold it actually feels on exposed skin when wind is factored in. As wind speed increases, it strips away the thin layer of warm air near your body and accelerates heat loss, making the air feel much colder than the thermometer reading. This calculator uses the official National Weather Service (NWS) 2001 wind chill formula, which is the standard used across the United States and Canada (in US units of °F and mph).
How to Use It
Enter the current air temperature in degrees Fahrenheit and the sustained wind speed in miles per hour. The calculator returns the wind chill — the "feels like" temperature. The NWS formula is defined for air temperatures at or below 50 °F and wind speeds above 3 mph; outside that range wind chill is essentially equal to the air temperature, so the tool simply returns the air temperature in those cases.
The Formula Explained
The equation is $$T_{wc} = 35.74 + 0.6215\,\text{T} - 35.75\,\text{V}^{0.16} + 0.4275\,\text{T}\,\text{V}^{0.16}$$ where \(T\) is air temperature in °F and \(V\) is wind speed in mph. The \(V^{0.16}\) term captures how wind's cooling effect grows quickly at first and then levels off — doubling the wind does not double the chill.
Worked Example
For \(T = 35\) °F and \(V = 10\) mph: \(V^{0.16} = 10^{0.16} \approx 1.44544\). Then $$WC = 35.74 + 0.6215\times 35 - 35.75\times 1.44544 + 0.4275\times 35\times 1.44544 \approx 35.74 + 21.7525 - 51.6745 + 21.6280 \approx 27.45 \text{ °F}$$ So 35 °F with a 10 mph wind feels like roughly 27 °F.
FAQ
Does humidity affect wind chill? No. Wind chill only uses temperature and wind speed. Humidity matters for the heat index in hot weather, not wind chill.
Why does it match the air temperature sometimes? When the wind is 3 mph or less, or the temperature is above 50 °F, the NWS formula is not applied and the feels-like value equals the air temperature.
Can wind chill cause frostbite? Yes. At low wind chill values, exposed skin can freeze in minutes, which is why the NWS issues wind chill warnings.
