Wind chill index

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Canada's wind chill index

Canada's wind chill index is accurate, easy to understand and reflects the needs of Canadians. It uses research from human volunteers and advanced computer technology combined with recent medical advances. This assists in the understanding of how the body loses heat when exposed to cold. As a result, the wind chill observations and forecasts that you hear are now much more representative of what you actually feel.

The index is displayed in temperature-like units, the format preferred by most Canadians. By equating the outdoor conditions to an equivalent temperature with no wind, the index represents the degree of "chill" that your skin senses. For example, if the wind chill is -20 while the outside temperature is only -10ºC, it means that your face will feel as cold as if it was a calm day (no wind) with a temperature of -20ºC.

The wind chill index allows Canadians to learn the best ways to avoid injuries from the cold. This includes dressing warmly to avoid frostbite and hypothermia. As well as  making informed decisions based on accurate wind chill information, such as whether it is safe for children to play outdoors.

On cold and blustery winter days, listen for the wind chill index in your local weather forecast.

Weather information

What is wind chill?

Anyone who has ever waited at a bus stop or taken a walk on a blustery winter day knows that you feel colder when the wind blows. We call the cooling sensation that is caused by the combined effect of temperature and wind, the wind chill.

On a calm day, our bodies insulate us somewhat from the outside temperature by warming up a thin layer of air close to our skin, known as the boundary layer. When the wind blows, it takes this protective layer away, exposing our skin to the outside air. It takes energy for our bodies to warm up a new layer. If each layer keeps getting blown away, our skin temperature will drop and we will feel colder.

Wind also makes you feel colder by evaporating any moisture on your skin - a process that draws more heat away from your body. Studies show that when your skin is wet, it loses heat much faster than when it is dry.

How does wind chill affect you?

Living in a cold country can be hazardous to your health. Each year in Canada, more than 80 people die from over-exposure to the cold, and many more suffer injuries resulting from hypothermia and frostbite. Wind chill can play a major role in such health hazards because it speeds up the rate at which your body loses heat.

How much heat you lose depends not only on the cooling effects of the cold and the wind chill, but on other factors as well. Good quality clothing with high insulating properties traps air, creating a thicker boundary layer around the body which keeps in the heat. Wet clothing and footwear lose their insulating properties, resulting in body heat loss nearly equal to that of exposed skin. Your body type also determines how quickly you lose heat: people with a tall, slim build become cold much faster than  those who are shorter and heavier.

In addition, we can also gain heat by increasing our metabolism or soaking up the sun.  Physical activity, such as walking or skiing, increases our metabolism - which generates more body heat. Age and physical condition also play a part. Elderly people and children have less muscle mass and, as a result, generate less body heat. Sunshine, even on a cold winter day, can also make a difference. Bright sunshine can make you feel as much as 10ºC warmer.

Over time, our bodies can also adapt to the cold. People who live in a cold climate are often able to withstand cold better than those from warmer climates.

Beating the chill

The best way to avoid the hazards of wind chill is to check the weather forecast before going outside and to prepare by dressing warmly. As a guideline, keep in mind that the risk of frostbite increases rapidly when wind chill values go below -27.

A simple way to avoid wind chill is to get out of the wind. Environment and Climate Change Canada's wind chill forecasts base their research on the wind you would experience on open ground. Taking shelter from the wind can reduce or even eliminate the wind chill factor. However, you would still feel cold from the outside temperature alone.

A recent survey indicated that 82% of Canadians use wind chill information to decide how to dress before going outside in the winter. Many groups and organizations use the wind chill index to regulate their outdoor activities. Schools use wind chill information to decide whether it is safe for children to go outdoors at recess. Hockey clubs cancel outdoor practices when the wind chill is too cold. People who work outside for a living, such as construction workers and ski-lift operators, are to take mandatory indoor breaks to warm up when the wind chill is very cold.

Seven steps to cold weather safety

1. Check the weather forecast

Environment and Climate Change Canada's weather forecasts are available through radio and TV broadcasts, Environment and Climate Change Canada's Weatheradio network, and online at:

Weather information

2. Plan ahead

(For example, schools could hold recess indoors, outside workers could schedule warm-up breaks and those involved in winter recreation could reduce the amount of time they spend outdoors.)

3. Dress warmly

4. Seek shelter

5. Stay dry

6. Keep active

7. Be aware

Cold injuries

Exposure to the cold can be hazardous or even life-threatening. Your body's extremities, such as the ears, nose, fingers and toes, lose heat the fastest. Exposed skin may freeze, causing frostnip or frostbite. In extreme conditions or after prolonged exposure to the cold, the body core can also lose heat, resulting in hypothermia.

Hypothermia

What to do:

Frostnip

What to do:

Frostbite

What to do:

Try this!

Turn on a fan. Stand in front of it. You will feel colder because of the wind cooling your skin, but the temperature in the room has not changed. You cannot make the room any colder, no matter how high you turn up the fan. Similarly, no matter how strong the wind blows, the temperature of the air outside does not change. Now dab some water on your skin. Stand in front of the fan again. The wet skin will feel much colder. This demonstrates how important it is to stay dry when outdoors in cold and windy conditions.

Canada's role in developing the wind chill index

Canada took the lead to promote an international standard for wind chill. In April 2000, Environment Canada held the first global Internet workshop on wind chill, with more than 400 participants from 35 countries. Almost all participants agreed on the need for an international standard for measuring and reporting wind chill. During 2001, a team of scientists and medical experts from Canada and the U.S. worked together to develop the current wind chill index. The research agency of the Canadian Department of National Defence, with its knowledge of how troops are affected by cold weather, contributed to the effort by conducting experiments using human volunteers. The wind chill index is based on the loss of heat from the face - the part of the body that is most exposed to severe winter weather. Volunteers were exposed to a variety of temperatures and wind speeds inside a refrigerated wind tunnel. They were dressed in winter clothing, with only their faces exposed directly to the cold. To simulate other factors affecting heat loss, they also walked on treadmills and were tested with both dry and wet faces. To ensure that the wind chill index met the needs of Canadians, Environment Canada conducted public surveys across the country. The current index expresses itself in temperature-like units because it is the format that was preferred by most Canadians. However, since the wind chill index is not actually a real temperature but, rather, represents the feeling of cold on your skin, it is reported without the degree sign. For example, "Today the temperature is -10ºC and the wind chill is -20."The same index is also used in the U.S. to ensure that travellers hear consistent information in both countries (although the U.S. index is provided on a Fahrenheit scale). 

Where is the coldest wind chill in Canada?

Wind chills below -70 have been recorded in northern communities in Canada. On January 13, 1975, at Kugaaruk, Nunavut, the air temperature was -51ºC and the winds were 56 km/h, producing a bone-chilling wind chill of -78.

Wind chill hazards

Wind chill hazards and what to do
Wind chill Exposure risk Health concerns What to do
0 to -9 Low Risk
  • Slight increase in discomfort
  • Dress warmly
  • Stay dry
-10 to -27 Moderate risk
  • Uncomfortable
  • Risk of hypothermia and frostbite if outside for long periods without adequate protection.
  • Dress in layers of warm clothing, with an outer layer that is wind-resistant.
  • Wear a hat, mittens or insulated gloves, a scarf and insulated, waterproof footwear.
  • Stay dry.
  • Keep active
-28 to -39 High risk: exposed skin can freeze in 10 to 30 minutes
  • High risk of frostnip or frostbite: Check face and extremities for numbness or whiteness.
  • High risk of hypothermia if outside for long periods without adequate clothing or shelter from wind and cold.
  • Dress in layers of warm clothing, with an outer layer that is wind-resistant
  • Cover exposed skin
  • Wear a hat, mittens or insulated gloves, a scarf, neck tube or face mask and insulated, waterproof footwear
  • Stay dry
  • Keep active
-40 to -47 Very high risk: exposed skin can freeze in 5 to 10 minutesFootnote1
  • Very high risk of frostbite: Check face and extremities for numbness or whiteness.
  • Very high risk of hypothermia if outside for long periods without adequate clothing or shelter from wind and cold.
  • Dress in layers of warm clothing, with an outer layer that is wind-resistant.
  • Cover all exposed skin.
  • Wear a hat, mittens or insulated gloves, a scarf, neck tube or face mask and insulated, waterproof footwear.
  • Stay dry
  • Keep active.
-48 to -54 Severe risk: exposed skin can freeze in 2 to 5 minutesFootnote1
  • Severe risk of frostbite: Check face and extremities frequently for numbness or whiteness.
  • Severe risk of hypothermia if outside for long periods without adequate clothing or shelter from wind and cold.
  • Be careful. Dress very warmly in layers of clothing, with an outer layer that is wind-resistant.
  • Cover all exposed skin
  • Wear a hat, mittens or insulated gloves, a scarf, neck tube or face mask and insulated, waterproof footwear.
  • Be ready to cut short or cancel outdoor activities.
  • Stay dry.
  • Keep active.
-55 and colder Extreme risk: exposed skin can freeze in less than 2 minutesFootnote1
  • DANGER! Outdoor conditions are hazardous.
  • Stay indoors.

How to estimate wind chill values

  1. Estimate the wind speed outside by observing the movement of trees and flags, using the guide provided in the table below.
  2. Once you have estimated the wind speed and you know the temperature outside, you can estimate the wind chill by referring to the numerical chart below.
Wind chill index (temperature in °C)
Wind speed (km/h) Estimating wind speed - what to look for 0 - 5 -10 -15 -20 -25 -30 -35 -40 -45 -50
10 Wind felt on face - wind vane begins to move -3 - 9 -15 -21 -27 -33 -39 -45 -51 -57 -63
20 Small flags extended -5 -12 -18 -24 -30 -37 -43 -49 -56 -62 -68
30 Wind raises loose paper, large flags flap and small tree branches move -6 -13 -20 -26 -33 -39 -45 -52 -59 -65 -72
40 Small trees begin to sway and large flags extend and flap strongly -7 -14 -21 -27 -34 -41 -48 -54 -61 -68 -74
50 Large branches of trees move, telephone wires whistle
-8 -15 -22 -29 -35 -42 -49 -56 -63 -69 -76
60 Trees bend and walking against the wind is hard -9 -16 -23 -30 -36 -43 -50 -57 -64 -71 -78

Weather forecasts

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