Wind Chill Calculator
Calculate wind chill temperature from air temperature and wind speed. Includes frostbite risk time and cold weather safety levels based on NWS standards.
°C
km/h
Enter your values above to see the results.
Tips & Notes
- ✓Wind chill only applies to living tissue — it does not affect inanimate objects like car engines or water in pipes. A thermometer in wind reads actual air temperature; only skin temperature is affected by wind chill.
- ✓The 2001 NWS/Environment Canada formula is valid for temperatures at or below 50°F (10°C) and wind speeds above 3 mph (4.8 km/h). Below 3 mph, calm conditions apply and wind chill equals air temperature.
- ✓Frostbite time decreases exponentially with lower temperature and higher wind. At −20°F with 30 mph wind (wind chill −73°F), exposed skin can freeze in under 5 minutes. Always cover exposed skin when wind chill is below −15°F.
- ✓Wet clothing dramatically accelerates heat loss — wet fabric loses its insulating value and conducts heat 25× more effectively than dry fabric. Treat wet clothing in cold and wind as an immediate frostbite and hypothermia risk.
- ✓Layering works because trapped still air is an excellent insulator. Base layer wicks moisture; mid layer (fleece/down) traps warm air; outer layer blocks wind and precipitation. The wind chill effect penetrates only the wind-blocking outer layer.
Common Mistakes
- ✗Applying wind chill to objects or water — wind chill is a human physiological index. A car radiator, water pipe, or exposed metal does not cool to wind chill temperature; it cools to actual air temperature at best.
- ✗Using wind chill as the actual temperature for non-biological purposes — wind chill of −30°F with actual temperature of 0°F means your skin cools as fast as it would in still air at −30°F. The thermometer still reads 0°F.
- ✗Ignoring that sun exposure partially offsets wind chill — the NWS formula assumes overcast conditions or shade. Direct winter sunlight can add 10-15°F of apparent warmth, partially offsetting the wind chill effect on skin.
- ✗Underestimating frostbite risk at moderate wind chills — frostbite can occur at wind chills above −20°F, especially in wet conditions, with wet clothing, or in individuals with poor circulation. Monitor exposed skin color (white or gray) rather than relying only on temperature thresholds.
- ✗Assuming wind chill affects time to freeze a water pipe — pipe freezing depends on actual air temperature maintained over time, not wind chill. Pipes exposed to −10°F actual temperature with no wind are at greater freeze risk than pipes at 20°F actual temperature with high wind.
Wind Chill Calculator Overview
Wind chill quantifies the accelerated heat loss from exposed human skin caused by wind. Still cold air allows a thin insulating layer of warm air to remain next to the skin; wind constantly replaces this warm boundary layer with cold air, dramatically increasing the rate of heat loss and skin cooling.
NWS Wind Chill formula (2001):
WC (°F) = 35.74 + 0.6215T − 35.75V^0.16 + 0.4275T × V^0.16 | Valid for T ≤ 50°F, V ≥ 3 mph
EX: T = 5°F, V = 25 mph → WC = 35.74 + 0.6215×5 − 35.75×25^0.16 + 0.4275×5×25^0.16 = 35.74 + 3.11 − 35.75×1.741 + 2.138×1.741 = 35.74 + 3.11 − 62.24 + 3.72 = −19.7°F (frostbite in under 30 min)Metric formula (°C, km/h):
WC (°C) = 13.12 + 0.6215T − 11.37V^0.16 + 0.3965T × V^0.16 | Valid for T ≤ 10°C, V ≥ 4.8 km/h
EX: T = −10°C, V = 40 km/h → WC = 13.12 + 0.6215×(−10) − 11.37×40^0.16 + 0.3965×(−10)×40^0.16 = 13.12 − 6.215 − 11.37×1.741 + (−3.965×1.741) = 13.12 − 6.215 − 19.79 − 6.90 = −19.8°CWind chill table (°F) — temperature vs. wind speed:
| Temp / Wind | 5 mph | 10 mph | 20 mph | 30 mph | 40 mph |
|---|---|---|---|---|---|
| 40°F | 36°F | 34°F | 30°F | 28°F | 27°F |
| 30°F | 25°F | 21°F | 17°F | 15°F | 13°F |
| 20°F | 13°F | 9°F | 4°F | 1°F | −1°F |
| 10°F | 1°F | −4°F | −9°F | −12°F | −15°F |
| 0°F | −11°F | −16°F | −22°F | −26°F | −29°F |
| −10°F | −22°F | −28°F | −35°F | −39°F | −43°F |
| −20°F | −34°F | −41°F | −48°F | −53°F | −57°F |
| Wind Chill | Frostbite Time | Risk Category | Recommended Action |
|---|---|---|---|
| Above 16°F | No significant risk | Low | Normal cold weather clothing |
| −5 to 15°F | 30+ minutes | Moderate | Cover exposed skin |
| −20 to −5°F | 30 minutes | High | Limit outdoor time, full coverage |
| −35 to −20°F | 10 minutes | Very High | Avoid outdoor exposure |
| Below −35°F | 5 minutes | Extreme Danger | Emergency precautions only |
Frequently Asked Questions
The NWS 2001 formula: WC = 35.74 + 0.6215T − 35.75V^0.16 + 0.4275T × V^0.16, where T is temperature in °F and V is wind speed in mph. Example: T = 10°F, V = 20 mph → WC = 35.74 + 0.6215×10 − 35.75×20^0.16 + 0.4275×10×20^0.16 = 35.74 + 6.215 − 35.75×1.698 + 4.275×1.698 = 35.74 + 6.215 − 60.66 + 7.26 = −11.4°F. The 10°F actual temperature feels like −11°F on exposed skin.
NWS wind chill danger thresholds: Wind chill above 32°F — no significant cold stress. 16 to 32°F — uncomfortable, appropriate clothing needed. −5 to 15°F — very cold, frostbite possible on extended exposure. −20 to −5°F — Frostbite danger in 30 minutes or less on exposed skin. −35 to −20°F — Extreme danger, frostbite in 10 minutes or less. Below −35°F — Extreme danger, frostbite in 5 minutes or less on exposed skin. These thresholds assume average skin sensitivity; individuals with poor circulation, diabetes, or Raynaud's disease are at risk at higher temperatures.
Frostbite time table for exposed skin: Wind chill −10°F — 30 minutes. Wind chill −20°F — 20 minutes. Wind chill −30°F — 10 minutes. Wind chill −40°F — 5 minutes. Wind chill −50°F — 3 minutes or less. Wind chill below −60°F — less than 2 minutes. Frostbite begins when skin temperature drops below 28°F (−2°C). The wind chill formula predicts the rate at which exposed skin cools toward air temperature. These times assume exposed skin (face, hands) with no moisture, average metabolism, and moderate physical activity.
Wind chill measures the rate of heat loss from exposed skin, which determines frostbite risk for extremities and face. Hypothermia is the dangerous drop in core body temperature (below 95°F / 35°C) and depends on total body heat balance — including insulation of clothing, metabolic heat generation (activity level), wet vs. dry conditions, and duration of exposure. A person in a good sleeping bag at −40°F may not develop hypothermia; a person with wet clothing at 35°F with wind may develop it quickly. High wind chill increases hypothermia risk by increasing heat loss, but clothing, activity, and moisture are equally important factors.
The wind chill formula is based on the heat transfer physics of moving air over a heated surface (skin). At very low wind speeds (under 3 mph), the boundary layer of still air near the skin provides significant insulation — the actual heat transfer mechanism is less affected by the slight air movement. The 2001 formula was developed assuming a wind speed of at least 3 mph at face height (about 5 feet), which matches real-world walking conditions. Below 3 mph, the formula extrapolates poorly. At exactly 0 mph (calm), wind chill equals actual air temperature by definition, since there is no wind-enhanced heat loss.
For wind chills below −20°F: cover all exposed skin — face mask or balaclava protecting nose and cheeks, goggles over eyes, mittens (not gloves — mittens keep fingers together for better warmth) over liner gloves, waterproof outer layer. Wool and synthetic fleece retain warmth when wet; cotton does not (jeans and cotton socks are dangerous in cold wet conditions). Check extremities regularly — toes, fingers, nose, ears, cheeks. Early frostbite (frostnip): skin turns red and painful. Developing frostbite: skin turns white or grayish-yellow, waxy, hard, and numb. Rewarm frostnip by contact with warm skin; do not rewarm deep frostbite in the field — seek medical care.