Wind chill is the perceived temperature when wind makes the air feel colder than the actual air temperature. Understanding how to calculate it helps you dress appropriately and assess hypothermia risk.
The Wind Chill Formula
The formula adopted by the US National Weather Service and Environment Canada in 2001:
Wind chill (°C) = 13.12 + 0.6215T − 11.37V^0.16 + 0.3965T × V^0.16
Where:
- T = Air temperature in °C
- V = Wind speed in km/h
Example: Temperature −5°C, wind speed 30 km/h:
Wind chill = 13.12 + 0.6215(−5) − 11.37(30^0.16) + 0.3965(−5)(30^0.16)
= 13.12 − 3.108 − 11.37(1.857) + (−1.9825)(1.857)
= 13.12 − 3.108 − 21.12 − 3.68
= −14.8°C
With −5°C air and 30 km/h wind, it feels like −14.8°C.
Wind Chill Quick Reference Table
| Air temp | 10 km/h | 20 km/h | 30 km/h | 40 km/h | 50 km/h |
|---|---|---|---|---|---|
| 5°C | 3°C | 1°C | 0°C | −1°C | −1°C |
| 0°C | −3°C | −5°C | −7°C | −8°C | −9°C |
| −5°C | −9°C | −12°C | −14°C | −15°C | −17°C |
| −10°C | −15°C | −19°C | −21°C | −23°C | −25°C |
| −15°C | −21°C | −25°C | −28°C | −30°C | −32°C |
Fahrenheit Version
Wind chill (°F) = 35.74 + 0.6215T − 35.75V^0.16 + 0.4275T × V^0.16
Where T is in °F and V is wind speed in mph.
Frostbite Risk
| Wind chill | Frostbite risk |
|---|---|
| −10 to −27°C | Possible after prolonged exposure |
| −28 to −39°C | Frostbite possible in 10–30 minutes |
| −40 to −47°C | Frostbite possible in 5–10 minutes |
| −48°C and below | Frostbite in 2 minutes or less |
What Wind Chill Doesn't Measure
Wind chill describes the felt temperature on exposed skin — it does not:
- Affect the temperature of inanimate objects (your car will not freeze faster due to wind chill)
- Apply on sunny days with full sun exposure
- Account for humidity (the formula assumes dry skin)
Heat Index: The Summer Equivalent
In summer, heat index (also called "apparent temperature") accounts for how humidity makes temperatures feel hotter — the inverse of wind chill.
Heat index rises when humidity is high because sweat evaporates less efficiently.
Both wind chill and heat index are measures of human thermal comfort, not physical temperature.