Wind Chill Calculator: NWS Formula & Frostbite Risk
Find how cold it really feels from air temperature and wind speed. NWS/Environment Canada formula. Frostbite time estimates (5, 10, 30 min). Free wind chill calculator.
How Wind Chill Works
Wind chill is the apparent temperature when wind blows across exposed skin—the "feels like" reading that reflects heat loss rate. The NWS/Environment Canada formula: with T in °F and v in mph. Wind removes the warm boundary layer next to your skin, increasing heat loss. The index assumes a human face model at 5 feet, clear night, no sun.
Formula Limits: When Wind Chill Applies
The formula applies only when air temperature is ≤ 50°F (10°C) and wind speed is > 3 mph (4.8 km/h). Warmer temps or calm air fall outside the model—use the actual temperature. The calculator flags out-of-range inputs.
Frostbite Time Estimates
At 0°F with 15 mph wind, wind chill is -19°F and exposed skin can freeze in about 30 minutes. Colder wind chills shorten the time: below -35°F, frostbite can occur in roughly 5 minutes. Hypothermia—a drop in core body temperature below 95°F—can develop before frostbite and is life-threatening.
Wind Chill vs Actual Temperature
Wind chill cannot lower an object below air temperature. It only affects how quickly you reach that temperature. If it's 35°F with a wind chill of 20°F, water pipes will not freeze—the air is still above 32°F. For humans, wind increases heat loss because we're trying to maintain 98.6°F; for inanimate objects, wind only speeds how fast they equilibrate to the ambient temperature.
Wind Chill Calculator FAQ
? What is wind chill?
Wind chill is the "feels like" temperature when wind blows across exposed skin—how cold it actually feels, not the thermometer reading. The NWS/Environment Canada formula: where T is air temp (°F) and v is wind speed (mph). Wind strips the warm boundary layer from your skin, so you lose heat faster.
? When does the wind chill formula apply?
Only when air temperature is ≤ 50°F (10°C) and wind speed is > 3 mph (4.8 km/h). Above 50°F or in calm air, the model doesn't apply—use the actual temperature instead. The calculator shows "Formula Out of Range" when inputs fall outside these limits.
? Can wind chill freeze water pipes?
No. Wind chill cannot lower an object's temperature below the actual air temperature. If it's 35°F outside with a wind chill of 20°F, your pipes won't freeze—the air is still above 32°F. Wind chill affects how quickly you cool toward that temperature. For humans, that means faster heat loss; for inanimate objects, it only speeds how fast they reach air temp.
? What do the frostbite risk levels mean?
NWS guidelines: Low (> 5°F wind chill) = no immediate threat. Moderate (-19°F to 5°F) = frostbite possible in ~30 min. High (-35°F to -20°F) = ~10 min. Extreme (< -35°F) = ~5 min, with high hypothermia risk. Hypothermia—a drop in core temp below 95°F—can develop before frostbite.
? How is wind chill different from heat index?
Both are "feels like" measures. Wind chill combines cold air and wind to estimate how quickly you lose heat. Heat index combines heat and humidity to estimate how hot it feels when sweat can't evaporate. Both use NWS-developed formulas.