Wind Chill Reference Chart (°F)
| Temp\Wind | 5 mph | 10 | 15 | 20 | 30 | 40 |
|---|---|---|---|---|---|---|
| 40°F | 36 | 34 | 32 | 30 | 28 | 27 |
| 30°F | 25 | 21 | 19 | 17 | 15 | 13 |
| 20°F | 13 | 9 | 6 | 4 | 1 | -1 |
| 10°F | 1 | -4 | -7 | -9 | -12 | -15 |
| 0°F | -11 | -16 | -19 | -22 | -26 | -29 |
| -10°F | -22 | -28 | -32 | -35 | -39 | -43 |
| -20°F | -34 | -41 | -45 | -48 | -53 | -57 |
Frostbite Risk Levels
| Wind Chill | Risk | Frostbite Time |
|---|---|---|
| Above 0°F | Low | Unlikely with proper clothing |
| 0°F to -10°F | Moderate | 30+ minutes on exposed skin |
| -10°F to -25°F | High | 10-30 minutes |
| -25°F to -45°F | Very High | 5-10 minutes |
| Below -45°F | Extreme | Under 5 minutes |
The NWS Wind Chill Formula
Adopted in 2001 by the National Weather Service and Meteorological Service of Canada, the current formula replaced the older Siple-Passel model from 1945. The older model overestimated cold danger because it was calibrated on a 33g plastic cylinder, not human skin. The 2001 revision used human trial data from volunteers at the University of Manitoba and Duke University walking into wind at various temperatures.
The formula only applies when temperature is 50°F or below and wind speed is above 3 mph. In calm conditions, the "feels like" temperature equals the actual temperature.