Wind chill: how it is calculated and what it means
Wind chill describes how cold the air feels on bare skin when the wind blows. At -20 °C with a 30 km/h wind, the index is -33: your face loses heat about as fast as in still air at -33 °C.
Updated November 7, 2026 · Sources
How the index is calculated
Environment and Climate Change Canada uses one equation for winds of 5 km/h or more and another for lighter winds. Both take the air temperature and the wind speed measured at the standard height of weather stations, which is why the index can differ from the wind you feel at street level.
The index is not a temperature that a thermometer could read: it compares the heat loss of your skin with what it would be in calm air. The US National Weather Service publishes the same index for air at 50 °F (10 °C) or colder.
Wind chill chart
Read the row of the air temperature, then the column of the wind speed. Every value comes from the same equation as our calculator.
| Air | 10 km/h | 20 km/h | 30 km/h | 40 km/h | 50 km/h | 60 km/h |
|---|---|---|---|---|---|---|
| 5 °C | 3 | 1 | 0 | -1 | -1 | -2 |
| 0 °C | -3 | -5 | -6 | -7 | -8 | -9 |
| -5 °C | -9 | -12 | -13 | -14 | -15 | -16 |
| -10 °C | -15 | -18 | -20 | -21 | -22 | -23 |
| -15 °C | -21 | -24 | -26 | -27 | -29 | -30 |
| -20 °C | -27 | -30 | -33 | -34 | -35 | -36 |
| -25 °C | -33 | -37 | -39 | -41 | -42 | -43 |
| -30 °C | -39 | -43 | -46 | -48 | -49 | -50 |
| -35 °C | -45 | -49 | -52 | -54 | -56 | -57 |
| -40 °C | -51 | -56 | -59 | -61 | -63 | -64 |
Environment Canada's risk levels
Environment Canada links each range of the index to a risk of frostbite and hypothermia:
- Low risk: 0 … -9.
- Moderate risk: -10 … -27.
- High risk: -28 … -39.
- Very high risk: -40 … -47.
- Severe risk: -48 … -54.
- Extreme risk: -55 and colder.
Good to know
Above 0 °C, Environment Canada does not publish a wind chill: there is no risk of frostbite.
Sun, dry clothing and shelter from the wind all reduce heat loss; wet skin and long exposure increase it. The index gives a common scale, not a personal diagnosis.