Wind Chill in Canada: How Is It Actually Calculated?

Wind chill is how cold the air feels on exposed skin once the wind is factored in. Environment and Climate Change Canada (ECCC) calculates it from the air temperature and the wind speed with a formula Canada introduced in 2001, developed with scientists in the United States and tested on volunteers. It is written without a degree sign: if the temperature is -10 °C and the wind chill is -20, your face feels about as cold as it would on a calm day at -20 °C.

How is wind chill calculated in Canada?

ECCC's standard formula, used when the air temperature is 0 °C or below and the wind is 5 km/h or more, is:

W = 13.12 + 0.6215 T − 11.37 V^0.16 + 0.3965 T V^0.16

Here W is the wind chill index, T is the air temperature in degrees Celsius, and V is the wind speed in kilometres per hour at 10 metres, the standard anemometer height.

ECCC's historical climate data glossary also lists a second, simpler equation for light winds, above 0 but below 5 km/h: W = T + [(−1.59 + 0.1345 T) / 5] × V. You will not see it in a forecast or in current conditions, because ECCC only includes wind chill there once the wind reaches 5 km/h, so the light-wind equation applies only where ECCC uses it below that speed.

Three worked examples from ECCC's own wind chill page:

Where did the formula come from?

Environment Canada led the work, starting with an online workshop on wind chill in the spring of 2000, and a team of scientists and medical experts from Canada and the United States developed the formula over two years. It was tested in the spring of 2001 at the Department of National Defence's Defence and Civil Institute of Environmental Medicine in Toronto. Six men and six women aged 22 to 42 walked on a treadmill at 4.8 km/h into wind of 10, 20 and 30 km/h in a refrigerated wind tunnel, at 10, 0 and -10 °C, with heat-flow sensors on their faces. To protect the people most at risk of frostbite, the model was based on the 5% of the population whose faces cool fastest. Canada launched the new index that fall, and the US National Weather Service uses the same index.

The index it replaced was about 60 years old and had been estimated from heat loss from cylinders of water in the Antarctic, with winds measured on towers more than 10 metres above the ground. The new formula still takes the standard 10-metre wind but calculates the wind at face height, about 1.5 metres, where friction cuts the speed to roughly two thirds. Environment Canada found the old index had slightly overstated wind chill.

Why does wind make it feel colder?

On a calm day your body keeps a thin layer of warm air next to your skin. Wind blows that layer away and dries the moisture off your skin, so you lose heat faster and your body has to work harder to warm a new layer. Wet skin gets cold even quicker: in the 2001 trials, faces sprayed with water gave wind chills 5 to 10 degrees colder than dry tests at the same temperature.

Wind chill cannot make anything colder than the air. ECCC's example: if the air temperature is -20 °C and the wind chill is -30, objects outside will only cool to -20 °C. The wind does make people and objects lose heat faster, so a car engine left out in the wind cools down sooner, but never below the air temperature.

When does Environment Canada report wind chill?

• At 0 °C or below, with wind of 5 km/h or more, ECCC includes wind chill in current conditions and forecasts.
• Above zero it is not shown, because there is no risk of frostbite however windy it is, although you can still feel colder in the wind.
• Only for today, tonight and tomorrow. Wind chill is not part of the full seven-day forecast. If the morning and afternoon values differ a lot, ECCC gives two for the day, and when it is cold enough the forecast adds frostbite information.

Is wind chill the same as "feels like"? Not exactly. Wind chill is ECCC's cold-weather index and is only reported at 0 °C or below. In hot, humid weather ECCC uses a different index, the humidex, which it shows from 20 °C, so the two are never used at the same temperature. A "feels like" figure in an app may be calculated in other ways. The United States uses the same wind chill index in °F, explained in wind chill vs feels like in the US.

What wind chill is dangerous?

ECCC links each range of wind chill to a level of risk:

Two notes from ECCC. In sustained winds over 50 km/h, frostbite can happen faster than the table shows. And the risk of frostbite at a wind chill of -28 is the same as at an air temperature of -28 °C with no wind, but in the wind it sets in faster.

When does Environment Canada issue a cold warning?

ECCC does not issue wind chill warnings. It issues cold warnings, which include wind chill as part of the forecast, when the temperature or wind chill is expected to be much colder than normal and likely to affect your health. The level is different depending on where you live. Since 26 November 2025, every cold warning, like every ECCC weather alert, comes in yellow, orange or red. ECCC's Cold Impact Guide, which also covers Arctic outflow, describes three levels of impact: a risk, a very high risk and a severe risk of cold injury such as frostbite and hypothermia without adequate protection; at the extreme level, travel and outdoor activities are not safe. The colour combines the expected impact with how confident forecasters are, so a high-impact cold snap that forecasters are not yet sure of is yellow, not orange. How the colour is chosen is explained in our guide to Environment Canada's yellow, orange and red alerts.

What wind chill triggers a cold warning?

Before November 2025 ECCC listed the alert as an extreme cold warning and published fixed regional thresholds: the temperature or wind chill had to be expected to reach the value for at least two hours. The Weather Impact Guides now replace that table, but its last version (modified 3 July 2025) shows how much the trigger depended on place:

Coastal BC also had an Arctic outflow warning, for a wind chill of -20 or lower for 6 hours or more. Local health units still say what to expect. In October 2026, Lakelands Public Health, which covers Peterborough, Northumberland, Haliburton and Kawartha Lakes in Ontario, said ECCC generally issues cold warnings in its region when the temperature or wind chill is expected to reach -30 °C or colder for two or more consecutive hours. It added that most cold warnings are yellow, and that orange or red may be used for long cold spells or for cold rarely seen locally, such as -40 °C or colder.

What are the limits of the wind chill index?

• It models a face. The index is based on heat loss from the exposed face of someone walking at about 4.8 km/h into the wind, set for the 5% of people whose faces cool fastest.
• No sunshine. The US National Weather Service says the index assumes no effect from the sun, as on a clear night. Environment Canada noted in 2001 that warm winter sunlight has a major effect on how cold exposed skin feels.
• Dry skin. Wet skin cools faster; in the trials, wet faces gave wind chills 5 to 10 degrees colder.
• People differ. The 2001 trials found large differences in facial cooling between volunteers, and tall, thin people tend to feel the cold sooner than short, stocky ones.
• Strong wind. In sustained winds over 50 km/h, ECCC warns frostbite can come faster than its table shows.

How reliable is a forecast wind chill?

A forecast wind chill rests on two forecasts, temperature and wind, and the weather models behind the apps do not always agree on either. Our Canada forecast pages put Environment Canada's GEM model, the European ECMWF and the American GFS side by side with a forecast confidence line, and every city page lists each model's wind and feels-like value (the model's apparent temperature, not ECCC's wind chill). Our accuracy scoreboard grades each model on its daily high temperature and its daily maximum wind, plus whether it rained, over a rolling 30-day window. It does not grade the temperature in the colder hours of the day or wind chill itself, so treat it as a general guide to which model handles temperature and wind best, not as a wind chill score. If the models split on tomorrow's wind, treat a dramatic wind chill as uncertain. The cold warning itself is ECCC's call.

Wind chill turns air temperature and wind speed into one number for how fast exposed skin loses heat. It cannot cool anything below the air temperature, ECCC only reports it at 0 °C or below, and the risk table tells you how fast skin can freeze. When a cold warning is issued, the colour tells you how serious the impact is likely to be and how sure forecasters are: cover exposed skin and keep checking your face and fingers for numbness or whiteness.