It's 2°C outside. Not ideal, but manageable — you've dressed for it. Then you step out of the sheltered doorway and the wind hits you, and suddenly it feels more like -8°C. You weren't underdressed for the temperature. You were underdressed for the wind chill.
Wind chill is one of the most practically important numbers in cold-weather forecasting, and understanding it can be the difference between a comfortable winter outing and a genuinely dangerous situation.
Wind chill is the perceived decrease in air temperature felt by the body due to the flow of air across exposed skin. It doesn't change the actual air temperature — a thermometer on a windy day reads the same as on a calm day. What changes is how quickly the wind removes heat from your body.
Your body constantly generates heat and radiates a thin layer of warm air around your skin. This "boundary layer" acts as a natural insulator. When wind blows, it strips that warm layer away. The faster the wind, the more efficiently it removes your body heat, making you feel much colder than the thermometer suggests.
Wind chill only applies to living things — it has no effect on inanimate objects like car engines or water pipes, which will cool to the actual air temperature regardless of wind speed, but no lower.
The modern wind chill formula used by Environment Canada and the US National Weather Service was revised in 2001 following research on human heat loss. It's based on studies of walking humans at face height (1.5 metres) and accounts for the actual physiology of skin cooling.
The formula (in Celsius, with wind speed in km/h) is:
Wind Chill = 13.12 + 0.6215T − 11.37V0.16 + 0.3965T × V0.16
Where T is the air temperature in °C and V is the wind speed in km/h. You don't need to calculate this yourself — weather apps including ClearCast do it automatically — but it's worth knowing that the formula has a solid scientific basis, not just a rule of thumb.
| Air Temp | Wind Speed | Feels Like (Wind Chill) | Frostbite Risk |
|---|---|---|---|
| 0°C | Calm (0 km/h) | 0°C | Low |
| 0°C | 20 km/h | -5°C | Low |
| 0°C | 40 km/h | -8°C | Low–Moderate |
| 0°C | 60 km/h | -10°C | Moderate |
| -10°C | 40 km/h | -20°C | High — 30 min exposure risk |
| -20°C | 40 km/h | -33°C | Very High — frostbite in minutes |
Wind chill values below -10°C warrant extra caution for extended outdoor exposure, particularly for children and the elderly. Below -20°C, frostbite on exposed skin can occur within 30 minutes for most people. Below -35°C, frostbite risk escalates to under 10 minutes. Below -50°C — which can occur in Canada and parts of Russia during severe Arctic outbreaks — exposed skin can freeze in under two minutes.
Wind chill is only reported when temperatures are at or below 10°C. Above this threshold, wind actually feels pleasant — it assists in evaporative cooling and generally makes warm conditions more comfortable rather than more dangerous. The heat index (which accounts for humidity making heat feel worse) is the relevant measure at high temperatures instead.
Layer strategically: The outer layer should be windproof. A thin windproof shell dramatically reduces the stripping of your boundary layer heat. You don't necessarily need a thick jacket — you need a wind-blocking one.
Cover exposed skin: Wind chill acts on bare skin. A face covering, gloves, and a hat eliminate most of the frostbite risk on your extremities, which lose heat fastest.
Stay dry: Wet clothing loses its insulating properties almost entirely. If wind chill is severe, prioritise keeping dry over everything else.
Watch the forecast, not just the temperature: Always check wind speed alongside temperature in cold weather. A calm -5°C day is far more manageable than a -2°C day with 60 km/h gusts.
ClearCast displays the "Feels Like" temperature — which incorporates wind chill in cold conditions — prominently on every location's weather card. Before heading out in winter, check both the actual temperature and the feels-like value to dress appropriately and stay safe.
→ Check the wind chill feels-like temperature for your city now