Wind chill is how cold it feels on exposed skin when wind speeds up heat loss. The National Weather Service formula is 35.74 + 0.6215T − 35.75V^0.16 + 0.4275TV^0.16, with T in °F and V in mph, and it applies only at 50°F or colder with wind above 3 mph. At 20°F with a 15 mph wind, the wind chill is about 6°F. At 0°F with 15 mph wind it is −19°F, and the NWS says frostbite can occur on exposed skin in 30 minutes.
This wind chill calculator estimates how cold it feels when wind moves across exposed skin. Enter air temperature in Fahrenheit and wind speed in mph. The default 20°F with 15 mph wind returns about 6.22°F wind chill.
Check conditions before winter outdoor plans, then dress for the feels-like number rather than the calm air reading alone. For general unit conversion before you enter values, use the unit converter.
How the formula works
For cold, windy conditions the tool applies 35.74 + 0.6215T – 35.75×v^0.16 + 0.4275T×v^0.16. If T is above 50°F or wind is under 3 mph, it returns T unchanged.
Worked example
T = 20, v = 15. Both sit inside the formula window, so the wind chill evaluates to about 6.22.
| Input | Value |
|---|---|
| Air temperature | 20°F |
| Wind speed | 15 mph |
| Wind chill | about 6.22°F |
Wind chill chart (°F), NWS formula
| Air temp | 5 mph | 10 mph | 15 mph | 20 mph | 30 mph |
|---|---|---|---|---|---|
| 40°F | 36 | 34 | 32 | 30 | 28 |
| 30°F | 25 | 21 | 19 | 17 | 15 |
| 20°F | 13 | 9 | 6 | 4 | 1 |
| 10°F | 1 | −4 | −7 | −9 | −12 |
| 0°F | −11 | −16 | −19 | −22 | −26 |
| −10°F | −22 | −28 | −32 | −35 | −39 |
Computed with the NWS formula and rounded; it matches the NWS chart. Sources: NWS wind chill chart and NWS formula PDF.
How to use the fields
- Air temperature is the thermometer reading in °F.
- Wind speed is sustained wind in mph. Use sustained wind speed, as forecasts do, not gusts.
Validity window
Wind chill charts are built for cold air and meaningful wind. Warm breezes or nearly calm air do not use the same relation, which is why the calculator falls back to air temperature outside that window.
What wind chill does and does not mean (NWS)
| Point | Detail |
|---|---|
| Valid range | Air temperature at or below 50°F and wind above 3 mph |
| Frostbite | At a −19°F wind chill (0°F, 15 mph), frostbite exposed skin can freeze in 30 minutes |
| Above freezing | Frostbite needs actual air temperature below freezing, whatever the wind chill |
| Objects | Wind does not cool objects such as pipes or car radiators below the actual air temperature |
| Sunshine | Bright sunshine may increase the wind chill temperature by 10°F to 18°F |
Source: NWS wind chill chart. Follow local NWS warnings.
Common mistakes
- Entering Celsius in the Fahrenheit field
- Using km/h without converting to mph
- Treating wind chill as a measured air temperature
- Ignoring calm conditions where wind chill is not applied
Outdoor planning
A calm 20°F day and a windy 20°F day do not feel the same. Use the default style inputs to compare clothing needs when wind rises while the thermometer stays fixed.
Safety note
Wind chill is a planning aid, not a medical device. Frostbite risk also depends on exposure time, wet clothing, and individual factors the calculator does not model.
Wind chill assumes exposed skin. Covered skin changes heat loss. Use the number to plan layers, not to claim a precise body temperature.
Wet clothing worsens heat loss beyond what wind chill alone captures. Dry layers matter as much as the calculated feels like value.
Limitations
Fahrenheit and mph only. For warm-weather conditions, use the heat index calculator. No humidity term, no solar load, and no altitude adjustment. For moisture in the air, find the dew point from temperature and humidity with the dew point calculator.