Feels-Like Temperature
Last reviewed: May 2026
The wind chill index was developed by Antarctic explorers Paul Siple and Charles Passel in the 1940s and modernized by the NWS and Environment Canada in 2001.[1] Wind accelerates heat loss from exposed skin through convection. The faster the wind, the faster your body loses heat, lowering the effective temperature your skin experiences. This calculator uses the current NWS formula, which is calibrated to modern understanding of human facial skin cooling rates.
| Air Temp (°F) | 10 mph Wind | 20 mph Wind | 30 mph Wind | Frostbite Risk |
|---|---|---|---|---|
| 30 | 21°F | 17°F | 15°F | Low |
| 15 | 3°F | −2°F | −5°F | Moderate |
| 0 | −16°F | −22°F | −26°F | High (30 min) |
| −15 | −35°F | −42°F | −46°F | Severe (10 min) |
| −30 | −53°F | −61°F | −67°F | Extreme (5 min) |
| Temp (°F) | 10 mph | 20 mph | 30 mph | 40 mph |
|---|---|---|---|---|
| 40 | 34 | 30 | 28 | 27 |
| 30 | 21 | 17 | 15 | 13 |
| 20 | 9 | 4 | 1 | −1 |
| 10 | −4 | −9 | −12 | −15 |
| 0 | −16 | −22 | −26 | −29 |
| −10 | −28 | −35 | −39 | −43 |
| −20 | −41 | −48 | −53 | −57 |
The current NWS wind chill formula (adopted in 2001) is: WC = 35.74 + 0.6215T − 35.75(V^0.16) + 0.4275T(V^0.16), where T is air temperature in °F and V is wind speed in mph at 5-foot height (face level). The formula is valid when temperature is at or below 50°F and wind speed is above 3 mph. It was calibrated using human trials on facial skin cooling rates, making it more physiologically accurate than the original Siple-Passel formula from the 1940s. The previous formula overestimated wind chill severity — temperatures reported under the old system were often 10–15°F lower than the current formula produces for the same conditions.
Frostbite occurs when skin tissue freezes, typically beginning with the extremities — fingers, toes, nose, ears, and cheeks. The NWS wind chill chart includes frostbite risk zones. At wind chills of −18°F to −32°F (the "moderate risk" zone), frostbite can develop on exposed skin within 30 minutes. Between −33°F and −49°F, frostbite risk drops to 10–30 minutes. Below −50°F, frostbite can occur in as little as 5 minutes. The first symptom is frostnip — numbness and white or grayish-yellow skin patches. Frostbite progresses through superficial (affecting skin surface) to deep (affecting muscles, tendons, and potentially bone), with deep frostbite carrying risk of permanent tissue damage and amputation. Moving indoors, removing wet clothing, and gradually warming the affected area in lukewarm (not hot) water are the recommended first-aid responses.
While wind chill specifically measures perceived cold on exposed skin, hypothermia — a dangerous drop in core body temperature below 95°F (35°C) — can develop at surprisingly mild temperatures when wet, fatigued, or inadequately dressed. Most hypothermia cases occur at temperatures between 30–50°F, not in extreme cold, because people underestimate the risk and dress insufficiently. Wind dramatically accelerates heat loss: a person in 35°F air with 25 mph wind (wind chill 23°F) loses body heat far faster than in calm 35°F air. Layering with moisture-wicking base layers, insulating mid-layers, and windproof outer shells is the most effective protection strategy. Cotton is particularly dangerous in cold weather because it absorbs moisture and loses its insulating properties when wet — the outdoor survival saying "cotton kills" reflects this real danger.
Wind chill and heat index are complementary "feels like" metrics for opposite ends of the temperature spectrum. Wind chill measures the cooling effect of wind in cold conditions, applying below 50°F with wind above 3 mph. Heat index measures the combined effect of heat and humidity above approximately 80°F, reflecting the body's reduced ability to cool itself through sweat evaporation when humidity is high. Both metrics express what the temperature "feels like" to the human body, but they measure different physiological processes — convective heat loss for wind chill and evaporative cooling efficiency for heat index. Most weather apps and forecasts report whichever metric is relevant to current conditions. For warm weather calculations, use our Heat Index Calculator.
→ Check wind chill before outdoor activities. Running, cycling, and skiing create additional wind chill from your own speed — a cyclist at 20 mph in 30°F calm air experiences a wind chill equivalent to about 17°F.
→ Cover exposed skin below 0°F wind chill. Frostbite risk becomes significant below 0°F wind chill. Cover face, fingers, and ears with insulating layers.
→ Wind chill does not affect objects. Your car, pipes, and buildings cool to the actual air temperature, never below it. Wind just makes them reach that temperature faster.
See also: Temperature Converter · Wind Speed Converter · Speed of Sound · Unit Converter
Runners, cyclists, and skiers generate additional wind chill through their own speed. A runner moving at 8 mph into a 10 mph headwind experiences an effective wind speed of 18 mph on exposed skin. A cyclist at 20 mph in calm 30°F air faces the same wind chill as standing still in 30°F air with 20 mph wind — approximately 17°F. Cross-country skiers face the most extreme conditions among recreational athletes because they operate at high speeds in cold environments with exposed facial skin. For outdoor winter training, dress for the wind chill temperature, not the actual air temperature. Cover all exposed skin when wind chill drops below 0°F. Use moisture-wicking base layers because sweat-soaked cotton accelerates heat loss dramatically. Consider a balaclava or face covering when wind chill drops below −10°F to protect the nose, cheeks, and ears from frostbite.
Wind chill also affects equipment and logistics for outdoor winter events. Camera batteries lose charge 2–3× faster in cold conditions. Smartphones may shut down unexpectedly below 32°F as lithium-ion batteries lose capacity. Water bottles can begin freezing within 30 minutes at wind chills below 0°F. Race organizers for winter marathons and obstacle course races monitor wind chill forecasts to make course modification or cancellation decisions when frostbite risk becomes unacceptable for extended outdoor exposure.
Understanding wind chill is ultimately about making informed decisions regarding outdoor exposure time, clothing choices, and activity planning during cold weather. The combination of temperature and wind speed creates conditions far more dangerous than either factor alone — a mild 25°F day with 30 mph gusts produces a wind chill of 8°F, cold enough for frostbite on exposed skin within 30 minutes. Check the wind chill forecast, not just the temperature, before any extended outdoor activity during winter months.
Winter weather safety starts with awareness — checking both temperature and wind speed before heading outdoors, dressing in windproof layers, and knowing the signs of frostbite and hypothermia can prevent the most common cold-weather injuries and emergencies.
Always consult wind chill values — not just the air temperature reading — before planning extended outdoor activities during winter months, and remember that your own movement speed adds to the effective wind on your skin during running, cycling, and skiing.
→ Cover all exposed skin below −18°F wind chill. Frostbite can occur in under 30 minutes.[1]
→ Wind chill only applies at 50°F or below. Above 50°F, wind has minimal cooling effect on skin.
→ Layer clothing. Multiple thin layers trap air and insulate better than one thick layer.[2]
→ Check conditions before outdoor exercise. Use the Heat Index Calculator for summer workouts.
See also: Heat Index · Temperature Converter · Speed Converter · Pace Calculator