Complete guide
Wind chill calculator using the National Weather Service formula
Enter cold-air temperature and wind speed in your preferred units. Calculator24 converts them to the NWS equation and reports apparent temperature in both Fahrenheit and Celsius, the drop from air temperature and an exposure reference.
What wind chill measures
Wind chill expresses how cold exposed skin feels because moving air increases heat loss. It is an apparent-temperature index, not a new air temperature.
NWS wind chill equation
The U.S. equation uses Fahrenheit and miles per hour internally.
WCT=35.74+0.6215T−35.75V^0.16+0.4275TV^0.16Official calculation range
NWS defines the index only when air temperature is 50°F or lower and wind exceeds 3 mph. The calculator rejects inputs outside that range rather than extrapolating.
Worked 0°F example
With T=0 and V=15, substituting into the formula gives approximately −19°F, matching the NWS reference example.
Frostbite and interpretation
Danger depends on actual exposure, clothing, health and shelter. Frostbite requires actual air below freezing; wind chill does not make objects colder than the surrounding air.
Sun, height and model limits
The index models a human face, adjusts standard wind observations toward face height and assumes no warming from sun. NWS notes bright sun can make conditions feel warmer.
NWS reference examples
| Air temperature | Wind | Wind chill |
|---|---|---|
| 40°F | 10 mph | 34°F |
| 20°F | 15 mph | 6°F |
| 0°F | 15 mph | −19°F |
| −20°F | 20 mph | −48°F |
Frequently asked questions
What is wind chill?
An index of heat loss from exposed skin caused by cold air and wind.
When is the formula valid?
At 50°F or below with wind above 3 mph.
Does wind chill change actual air temperature?
No.
Can wind chill freeze a pipe below the air temperature?
No; it can speed cooling toward the actual air temperature.
Does sunshine affect the index?
The standard index assumes shade; sun can make exposure feel warmer.
Can I enter Celsius and km/h?
Yes. The engine converts to the official units and converts the result back.
What to keep in mind
The NWS index is defined only at air temperatures of 50°F or lower and wind speeds above 3 mph. It estimates heat loss from exposed human skin in shade and is not an actual thermometer temperature.
Results display up to 8 decimal places; exported numbers preserve calculation precision. This is a calculation summary, not an official certificate.