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How Wind Chill Is Calculated
The NWS Wind Chill formula is: WC = 35.74 + 0.6215T - 35.75(V^0.16) + 0.4275T(V^0.16), where T is air temperature in degrees Fahrenheit and V is wind speed in mph. The formula is valid for temperatures at or below 50°F and wind speeds above 3 mph.
Frostbite Risk Levels
Frostbite risk depends on wind chill: above 0°F is low risk. Between 0°F and -17°F, exposed skin can develop frostbite in 30 minutes. Between -18°F and -35°F, frostbite can occur in 10 minutes. Below -35°F, frostbite is possible in 5 minutes or less.
Wind Chill vs Actual Temperature
Wind chill describes how cold it feels on exposed skin, not the actual air temperature. Objects cannot cool below the actual air temperature, but wind accelerates heat loss from skin, making it feel colder and increasing the risk of hypothermia and frostbite.
Protecting Yourself in Cold Wind
Cover exposed skin with windproof layers. Wear insulated gloves, a hat, and a scarf or neck gaiter. Layer clothing to trap warm air. Watch for signs of frostbite (numbness, white or gray skin patches) and hypothermia (shivering, confusion, slurred speech).
Frequently Asked Questions
Wind chill below 0°F is dangerous. At -20°F wind chill, frostbite can develop on exposed skin in as little as 10 minutes. At -40°F wind chill, frostbite can occur in 5 minutes. Always check the wind chill before going outside in winter.
Wind chill only affects living things with body heat. Pipes and cars cool to the actual air temperature, not the wind chill temperature. However, wind speeds up heat loss from warm objects, so pipes may freeze faster in windy conditions.
The current NWS formula, adopted in 2001, is based on clinical trials and is considered accurate for most conditions. It applies when the temperature is 50°F or below and wind speed is above 3 mph. In calm winds, the wind chill equals the air temperature.
There is no theoretical lower limit, but the lowest recorded wind chills on Earth have been around -100°F to -130°F in Antarctica. In the continental US, wind chills can reach -50°F to -70°F during severe Arctic outbreaks.