Wind Chill Calculator (NWS 2001)
Apparent temperature when wind cools exposed skin. Uses the NWS / Environment Canada 2001 formula (valid for T ≤ 50 °F, V ≥ 3 mph).
Result
- Air temperature20.0 °F
- Wind speed15.0 mph
- Wind chill (apparent)6.2 °F
- Cooling effect13.8 °F drop
- Frostbite-risk bandNo frostbite risk for normal exposure.
- FormulaNWS 2001: T_wc = 35.74 + 0.6215·T − 35.75·V⁰·¹⁶ + 0.4275·T·V⁰·¹⁶ (T in °F, V in mph)
Step-by-step
- Input: 20.0 °F, 15.0 mph.
- V⁰·¹⁶ = 15.0⁰·¹⁶ = 1.5423.
- Wind chill = 35.74 + 0.6215·20.0 − 35.75·1.542 + 0.4275·20.0·1.542 = 6.22 °F = -14.32 °C.
How to use this calculator
- Enter air temperature and wind speed at standard ground-level (10-m) conditions, or from the nearest weather station.
- Pick US or metric units — the calculator handles the conversion to the underlying NWS formula (which is defined in °F + mph).
- Wind chill is meaningless above 50 °F (10 °C) and below ~3 mph wind; the calculator warns in those cases.
About this calculator
Wind chill quantifies how much colder the air "feels" because wind strips heat from exposed skin faster than still air does. The current NWS / Environment Canada formula (2001 revision) replaced the older Siple-Passel (1945) formula that had been criticised for over-stating wind chill in light winds. The 2001 formula is calibrated by human-trial measurements of facial heat loss at 1.5 m height (5 ft) — about a human face level rather than the older 10 m anemometer height. Validity: air temperature ≤ 50 °F (10 °C) and wind ≥ 3 mph (4.8 km/h). At higher temps the wind has a cooling effect through evaporation rather than conductive heat loss, which is what the Heat Index measures instead. Frostbite-time bands (NWS): T_wc 0 to −18 °F = 30 min; −18 to −35 °F = 10 min; −35 to −60 °F = 5 min; below −60 °F = under 2 min.