The wind chill index tells you how cold it actually feels when wind is factored in. Uses the NWS/Environment Canada formula valid for temperatures at or below 50F and wind speeds above 3 mph.
Wind chill quantifies how cold the air feels on exposed skin once wind is factored in. Moving air strips warm air away from your skin faster than still air does, lowering skin temperature and increasing the rate of body-heat loss. A 20 °F day with 15 mph wind feels meaningfully colder than the same temperature on a calm day — and the U.S. National Weather Service publishes wind chill values precisely to communicate this risk.
This calculator uses the current NWS/Environment Canada wind chill formula (adopted in 2001, replacing the older Siple-Passel formula). It's valid for air temperatures at or below 50 °F and wind speeds above 3 mph. Below those thresholds, wind chill isn't reported; the air simply doesn't feel meaningfully colder than measured.
Wind chill matters most for frostbite risk. The NWS publishes frostbite-time charts based on wind chill: at −18 °F wind chill, frostbite can begin in 30 minutes on exposed skin; at −32 °F it can happen in 10 minutes; at −52 °F in 5 minutes. Wind chill is the right number for deciding when to keep kids inside, when to cancel outdoor work, or how long a winter run is safe.
Air temp: 30 °F Wind: 10 mph Wind chill: ≈ 21 °F About 9 °F colder than measured. Annoying for a long walk, not dangerous.
Air temp: −10 °F Wind: 25 mph Wind chill: ≈ −40 °F Frostbite in under 10 minutes on exposed skin. Closed schools, canceled outdoor work, and "shelter in place" warnings are common at this level.
Use wind chill to assess cold-weather exposure risk for skin and to plan outdoor activity duration. Wind chill is the relevant metric for: - Frostbite risk on exposed skin (face, hands) - Deciding when to cancel outdoor recess, sports, or work - Choosing winter clothing layers and duration of exposure - Travel risk during cold snaps (broken-down vehicles)
It does NOT apply to: - Pipe freezing: water freezes at the actual air temperature regardless of wind (though wind speeds up the process) - Indoor temperatures - Vehicle fluids: subject to actual air temperature, not wind chill - Plants: cold damage tracks actual air temperature plus radiative cooling
For warm-weather analogs, use the heat index (apparent temperature including humidity).
Calculate the heat index (feels-like temperature) from air temperature and humidity.
Calculate the dew point temperature from air temperature and relative humidity.
Estimate approximate sunrise and sunset times from your latitude and date.
Feels Like
6.2F
Danger Level
Low
Frostbite Risk
Low risk
| Detail | Value |
|---|---|
| Air Temperature | 20F (-6.7C) |
| Wind Speed | 15 mph |
| Wind Chill | 6.2F (-14.3C) |
| Feels Like Drop | 13.8F colder |
| Frostbite Risk | Low risk |
| Danger Level | Low |