Calculate the wind chill 'feels like' temperature and frostbite risk.
Wind chill describes how cold the air feels on exposed human skin due to the wind's convective heat loss. Moving air strips away the thin warm layer of air next to skin faster than calm air does, making the effective temperature feel colder. The NWS 2001 formula was developed from human trials where subjects walked outdoors at various temperatures and wind speeds, replacing the earlier 1945 formula that was derived from water-bottle experiments and consistently over-predicted the chill. The formula is valid only at or below 50°F (10°C) and at wind speeds above 3 mph (4.8 km/h); outside those bounds it produces unreliable results.
NWS 2001 Wind Chill (°F, mph)
Wind Chill = 35.74 + 0.6215 × T − 35.75 × V^0.16 + 0.4275 × T × V^0.16
The NWS 2001 formula was derived from experiments conducted in cold conditions with meaningful airflow. Extrapolating it to warm temperatures or calm air produces numbers that don't reflect actual cooling on human skin. Above 50°F, wind may feel pleasant but the formula would give a lower temperature than the air, which can mislead you into under-dressing.
The NWS frostbite risk bands are based on military and medical research into the time required for exposed skin to freeze. At −19°F wind chill, frostbite can occur in 30 minutes; at −38°F in 10 minutes; at −50°F in 5 minutes. These are guides, not guarantees — wet skin, prior cold injuries, and reduced circulation lower these thresholds.
No. Wind chill only applies to warm objects losing heat, like skin. It does not affect how cold a car engine gets, whether water pipes freeze, or whether a thermometer reads lower. A thermometer in the wind reads the true air temperature — the same number as a sheltered thermometer.
The NWS formula was published in US customary units (°F, mph). Converting inputs to °F and mph, computing the result, then converting back to °C is more accurate than using a metric reformulation, which introduces rounding. This calculator does exactly that conversion transparently.