Wind Chill Calculator
Calculate the NWS wind chill 'feels like' temperature and frostbite risk (valid ≤50°F, >3 mph).
Inputs
Formula valid at or below 50°F.
Formula valid above 3 mph.
Wind Chill (°F)
6.2
The 'feels like' temperature accounting for wind cooling.
Wind Chill (°C)
-14.3
Effective Temperature Drop (°F)
13.8
Frostbite Risk
Low — minimal frostbite risk under normal exposure.
Based on NWS exposure-time thresholds.
Step by step
Inputs (normalised to °F, mph)
= T = 20°F, V = 15 mph
Compute V^0.16
15^0.16
= 1.5423
Apply NWS 2001 formula
35.74 + 0.6215×20 − 35.75×1.5423 + 0.4275×20×1.5423
= 6.2°F (-14.3°C)
Effective temperature drop
20°F − 6.2°F
= 13.8°F (7.6°C)
Frostbite risk
= Low — minimal frostbite risk under normal exposure.
How it works
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.
Formula
NWS 2001 Wind Chill (°F, mph)
Wind Chill = 35.74 + 0.6215 × T − 35.75 × V^0.16 + 0.4275 × T × V^0.16
- T
- Air temperature in °F
- V
- Wind speed at 10 m height in mph
- WC
- Wind chill index in °F
Frequently Asked Questions
Why does the calculator refuse inputs above 50°F or below 3 mph?
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.
What is frostbite risk based on?
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.
Does wind chill affect the temperature of objects?
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.
Why does the formula use mph even for the metric version?
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.