Wind Chill Index Calculator
The wind chill index tells you how cold the outside air actually feels on exposed skin when wind speed is factored in. Wind removes the thin layer of warm air that surrounds your body, accelerating heat loss and making the effective temperature feel lower than the thermometer reading. The National Weather Service adopted the 2001 Joint Action Group (JAG) formula after field trials on human subjects, replacing the older Siple-Passel model. Enter the air temperature in degrees Fahrenheit and wind speed in mph to see the wind chill equivalent temperature and frostbite risk level.
Wind chill formula (NWS 2001)
WC = 35.74 + 0.6215T - 35.75(V^0.16) + 0.4275T(V^0.16)
Where T is air temperature in degrees Fahrenheit and V is wind speed in miles per hour. The formula is valid for T at or below 50 F and V above 3 mph. At lower wind speeds, wind chill approximates the actual air temperature.
Wind chill and frostbite risk
The NWS defines frostbite thresholds based on the calculated wind chill temperature:
- Wind chill above -17 F: no immediate frostbite risk in 30 minutes.
- Wind chill -18 F to -34 F: frostbite possible in 30 minutes for exposed skin.
- Wind chill -35 F to -59 F: frostbite possible in 10 minutes.
- Wind chill -60 F or below: frostbite possible in 5 minutes or less.
NWS issues wind chill watches and advisories when dangerous conditions are forecast. Cover all exposed skin and limit time outdoors when wind chills approach these thresholds.
Wind chill calculator: frequently asked questions
What formula does the NWS use for wind chill?
The National Weather Service adopted the 2001 Joint Action Group wind chill formula: WC = 35.74 + 0.6215T - 35.75(V^0.16) + 0.4275T(V^0.16), where T is air temperature in degrees Fahrenheit and V is wind speed in mph. It applies when T is at or below 50 F and V is above 3 mph.
Why does wind make it feel colder?
Wind increases the rate at which heat is carried away from exposed skin by accelerating convective cooling. Still air near the skin acts as an insulating layer; wind strips that layer away. The wind chill index quantifies this heat-loss effect as an equivalent air temperature.
When does the wind chill formula not apply?
Wind chill applies only when air temperature is 50 degrees F or below and wind speed exceeds 3 mph. In warmer conditions, the heat index is the appropriate metric. The formula also does not account for solar radiation, which can make exposed skin feel warmer than the wind chill value suggests.
What wind chill value is dangerous?
According to the NWS, frostbite can occur in 30 minutes when wind chill values reach -18 F, in 10 minutes at -35 F, and in as few as 5 minutes at -60 F or below. Hypothermia risk increases rapidly below 0 F wind chill. The NWS issues wind chill watches, advisories, and warnings based on these thresholds.
Does wind chill affect inanimate objects like pipes?
No. Wind chill only describes the cooling rate of exposed human (or animal) skin. Inanimate objects like water pipes or car engines cool to the actual air temperature, not to the wind chill temperature. However, they cool faster in wind than in calm conditions.
Official sources
- National Weather Service: Wind Chill Chart and Safety.
- NOAA/NWS: Wind Chill Calculator Reference.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.