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Calculate the wind chill temperature — how cold it actually feels with wind — from air temperature and wind speed. Find your frostbite risk time and get cold weather safety recommendations.
Wind removes the thin layer of warm air surrounding your skin, dramatically increasing heat loss from your body. A temperature of 20°F (-7°C) with 30 mph winds feels like -5°F (-21°C) — cold enough to cause frostbite in under 30 minutes. Wind chill is critical for outdoor safety in winter conditions.
Wind chill represents the rate of heat loss from exposed human skin caused by wind and cold. It does not affect inanimate objects — a car will not get colder than the actual air temperature due to wind. However, your body loses heat much faster in windy conditions, increasing frostbite and hypothermia risk dramatically.
| Wind Chill | Risk Level | Frostbite Time |
|---|---|---|
| Above -19°F (-28°C) | Low Risk | Frostbite in 30+ minutes of exposure |
| −19 to −37°F (−28 to −38°C) | High Risk | Frostbite in 10-30 minutes |
| −38 to −54°F (−39 to −48°C) | Very High Risk | Frostbite in 5-10 minutes |
| Below −54°F (−48°C) | Extreme Risk | Frostbite in 2-5 minutes |
Frostbite occurs when skin and underlying tissue freeze. Warning signs progress: Frostnip (redness, numbness, tingling) → Superficial frostbite (skin appears white or grayish-yellow, feels hard and waxy) → Deep frostbite (skin is hard, cold, blistering). Areas most vulnerable: fingers, toes, nose, ears, cheeks. Cover all exposed skin in dangerous wind chill conditions.
Three-layer system: Base layer (moisture-wicking synthetic or merino wool — never cotton, which retains moisture), middle layer (fleece or down insulation for warmth), outer shell (windproof and waterproof). Cover extremities: wool or synthetic socks, insulated waterproof boots, gloves or mittens (mittens are warmer), and a hat covering ears. 40-60% of body heat is lost through the head and neck.
The 2001 NWS wind chill formula replaced the original 1945 Siple-Passel formula for better accuracy. It is based on a model of the rate of heat loss from a human face in wind. The formula only applies when temperature is at or below 50°F (10°C) and wind speed is above 3 mph (5 km/h). Calm conditions (under 3 mph) show no wind chill effect.