Wind Chill Factor Calculator - Environmental Physics
Our meteorology & atmospheric science calculator computes wind chill factor environmental physics accurately. Get results you can export or share.
Reviewed by Daniel Agrici, Founder & Lead Developer
Formula
WCT = 13.12 + 0.6215T - 11.37V^0.16 + 0.3965TV^0.16
Where WCT is wind chill in C, T is air temperature in C, and V is wind speed in km/h at 10 m height. Valid for T at or below 10 C and V at or above 4.8 km/h.
Worked Examples
Example 1: Winter Storm Warning Assessment
Problem:Calculate wind chill for -10 C with 30 km/h winds at sea level and determine frostbite risk.
Solution:WCT = 13.12 + 0.6215*(-10) - 11.37*(30)^0.16 + 0.3965*(-10)*(30)^0.16\n= 13.12 - 6.215 - 11.37*1.879 + (-3.965)*1.879\n= 13.12 - 6.215 - 21.36 - 7.45 = -21.9 C\nApparent drop = -10 - (-21.9) = 11.9 C
Result:Wind Chill: -21.9 C | Danger: Increased Risk | Drop: 11.9 C
Example 2: Mountain Expedition at Altitude
Problem:Assess wind chill at 3000 m altitude with -20 C and 50 km/h winds.
Solution:WCT = 13.12 + 0.6215*(-20) - 11.37*(50)^0.16 + 0.3965*(-20)*(50)^0.16\n= 13.12 - 12.43 - 11.37*2.047 + (-7.93)*2.047\n= 13.12 - 12.43 - 23.27 - 16.23 = -38.8 C\nAltitude correction: -3.0 C\nAdjusted: -41.8 C
Result:Wind Chill: -38.8 C | Adjusted: -41.8 C | Frostbite in 5-10 min
Frequently Asked Questions
What is wind chill factor and how is it calculated?
Wind chill factor quantifies the combined cooling effect of air temperature and wind speed on exposed human skin expressed as an equivalent calm-air temperature producing the same heat loss rate. The current NWS formula adopted in 2001 is WCT = 13.12 + 0.6215T - 11.37V^0.16 + 0.3965TV^0.16 where T is Celsius and V is km/h at 10 meters height. It was derived from controlled human trials in refrigerated wind tunnels monitoring facial skin temperatures during walking. The model assumes walking speed of 5.4 km/h added to the wind and no direct sunlight on exposed skin. It replaced the older Siple-Passel index which overestimated cooling effects.
Why is wind speed raised to the power of 0.16?
The 0.16 exponent reflects the nonlinear relationship between wind speed and convective heat transfer from the human body. At low speeds increasing wind dramatically disrupts the insulating boundary layer of warm air on the skin surface. As speed increases further additional increments produce progressively smaller heat loss increases because the boundary layer is already largely destroyed. This diminishing return follows a power law determined empirically from wind tunnel experiments. Doubling the wind speed only increases the wind chill effect by about 12 percent rather than doubling it. This is consistent with engineering heat transfer correlations for convection from cylinders and flat plates.
What are the limitations of the wind chill index?
The wind chill index assumes clear night sky conditions with no sunshine so daytime with solar radiation feels warmer than indicated. The model is calibrated for exposed facial skin and does not account for clothing insulation on the rest of the body. It assumes 5.4 km/h walking speed and may overestimate cooling for stationary individuals. The formula is valid only for temperatures at or below 10 C and wind speeds at or above 4.8 km/h. Individual variation from body composition acclimatization age and health conditions is not captured in the standardized calculation.
How does wind chill relate to frostbite risk?
Frostbite occurs when skin tissue freezes due to rapid heat loss and the wind chill temperature predicts this risk at various thresholds. Between minus 10 and minus 27 C there is increased risk and exposed skin should be covered during outdoor activities. Between minus 28 and minus 39 C frostbite can develop within 10 to 30 minutes on exposed skin. From minus 40 to minus 47 C frostbite occurs in 5 to 10 minutes and below minus 48 C it develops in under 5 minutes. These thresholds are based on the time for facial skin to reach minus 4.8 C the onset temperature for superficial frostbite.
References
Reviewed by Daniel Agrici, Founder & Lead Developer · Editorial policy