The Chilling Facts about Wind Chill

In Canada , over 80 people die each year from over-exposure to the cold and many suffer injuries 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.

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 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, and if each one 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 much heat you lose depends not only on 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 that keeps in the heat. Wet clothing or footwear loses its insulated value, 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 that 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 and generates more body heat. Age and physical condition also play a part: elderly people and children have less muscle mass, so they 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 10 degrees 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.

The best way to avoid the hazards of wind chill is to check the weather forecast before going outside, and be prepared by dressing warmly. As a guideline, keep in mind that the average person’s skin begins to freeze at a wind chill of -25°C, and freezes in minutes at -35°C.

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 per cent of Canadians use wind chill information to decide how to dress before going outside in the winter. Many groups and organizations also use the system 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 required to take indoor breaks to warm up when the wind chill is very cold.

Seven Steps to Cold Weather Safety

Listen to the weather forecast

  • Check the Environment Canada weather forecast before going out in the cold.
  • If conditions are hazardous, a wind chill warning will be issued.
  • If the wind chill is very cold, exposed skin can freeze in minutes.

Plan Ahead

  • Groups and organizations should develop a plan in advance, to ensure that safety concerns are addressed when the wind chill is high. 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.

Dress warmly

  • Wear layers of warm clothing, with an outer jacket that is wind-resistant. Mittens, boots and a hat are also important. (We lose a large portion of our body heat from the head.)
  • When the wind chill is high, try to cover as much exposed skin as possible.
  • Wear a scarf, neck tube or face mask.
  • Check frequently for signs of frostbite.

Seek shelter

  • Get out of the wind.
  • When wind chill is very cold, limit the time you spend outside.

Stay dry

  • Wet clothing chills the body rapidly.
  • Remove outer layers of clothing or open your coat if you are sweating.

Keep Active

  • Walking or running will help keep you warm by generating body heat.

Know your limits

  • Some people are more susceptible to the cold, particularly children, the elderly and those with circulation problems.
  • The use of alcohol, tobacco and certain medications will increase your susceptibility to cold.

(Source: Defence R&D Canada, Defence and Civil Institute of Environmental Medicine – the research agency of the Canadian Department of National Defence)