Wind Chill Calculator
Discover how cold wind makes the air feel on your skin using air temperature and wind speed. Ideal for planning outdoor activities in winter or assessing frostbite risk.
About this calculator
Wind chill measures how fast exposed skin loses heat relative to still-air conditions. Moving air accelerates convective heat loss from the skin's surface, making cold temperatures feel even colder. The U.S. NWS and Environment Canada adopted a joint formula in 2001, valid for temperatures at or below 50 °F and wind speeds above 3 mph: WC = 35.74 + 0.6215·T − 35.75·V^0.16 + 0.4275·T·V^0.16, where T is the air temperature in °F and V is the wind speed in mph. The exponent 0.16 reflects the physics of boundary-layer heat transfer. At calm wind speeds the formula returns a value close to the actual air temperature. Wind chill does not affect inanimate objects like car engines or pipes — only living skin exposed to the wind.
How to use
Suppose the air temperature is 20 °F and the wind speed is 30 mph. Apply the formula: WC = 35.74 + (0.6215 × 20) − 35.75 × (30^0.16) + 0.4275 × 20 × (30^0.16). First, 30^0.16 ≈ 1.9690. Then: 35.74 + 12.43 − (35.75 × 1.9690) + (0.4275 × 20 × 1.9690) = 35.74 + 12.43 − 70.44 + 16.84 ≈ −5.4 °F. So a 20 °F day with 30 mph winds feels like −5 °F on exposed skin. Frostbite can occur in under 30 minutes at that level.
Frequently asked questions
What wind speed and temperature combination causes dangerous wind chill?
The NWS issues Wind Chill Advisories when the wind chill index reaches −15 °F to −24 °F, and Wind Chill Warnings at −25 °F or lower, as these levels can cause frostbite on exposed skin within 30 minutes or less. For example, 0 °F with a 20 mph wind produces a wind chill near −22 °F. At −10 °F with 30 mph winds, frostbite can develop in as few as 10 minutes. Children, elderly individuals, and anyone with circulatory problems face elevated risk and should limit time outdoors when wind chills are dangerously low.
How is the current wind chill formula different from the old one used before 2001?
Before 2001, both the U.S. and Canada used a formula derived from Antarctic researcher Paul Siple's 1940s experiments, which was based on cooling rates of a plastic cylinder of water — not human skin. That old formula tended to overestimate how cold wind feels, producing alarmingly low numbers that were not physiologically accurate. The 2001 NWS/Environment Canada formula was developed using human subjects in wind tunnels, clinical trials, and computer modeling of heat transfer from a realistic human face. It accounts for walking speed, actual skin resistance, and solar radiation adjustments, yielding more accurate and actionable results.
Why does wind chill not affect the temperature of objects like pipes or car engines?
Wind chill is a measure of heat loss rate from warm human skin, not a true physical lowering of air temperature. An inanimate object like a metal pipe or a car engine can only cool down to the actual ambient air temperature — wind just makes it reach that equilibrium faster. Once the object matches the air temperature, wind has no further cooling effect. For this reason, a water pipe will freeze if air temperature drops below 32 °F regardless of wind speed, and antifreeze must be rated to the actual air temperature, not the wind chill value.