Winter weather hazards
Winter is a naturally hazardous season in Canada because of its extremely cold temperatures, challenging driving conditions, and often severely hazardous winter storms.
Follow the links below to find out more about Canada’s winter weather hazards:
In addition to being careful when severe winter weather strikes, people should remember to exercise caution when travelling in potentially hazardous winter environments, such as across frozen bodies of water and in avalanche zones.
You may also wish to visit Environment Canada’s archive of climate and historical weather for a look at significant past events and trends in winter severe weather.
A blizzard is severe winter weather characterized by strong winds, and heavy or blowing snow that causes low to zero visibility. In whiteout conditions associated with blizzards people have become lost even when going only short distances. In Canada, blizzards occur most often in the southern Prairies, the Atlantic region, and the eastern Arctic.
Freezing Rain and Ice Pellets
Freezing rain or freezing drizzle is precipitation that falls in liquid form at first but then falls through a layer of cold air. If this layer of cold air is thick enough and the air temperature is below freezing, the precipitation freezes on contact with the ground (or an object that is below freezing temperature), forming a coating of ice on its surface.
Driving, and even walking can be dangerous in such conditions. As well, ice coated utility lines or poles can be brought down due to the excess weight of the ice.
Ice pellets are raindrops that freeze before they reach the ground, usually after falling through a very thick layer of air that is below freezing.
Unlike the more familiar fog, which reduces visibility due to suspended water droplets, ice fog reduces visibility due to suspended ice crystals. Ice fog occurs at very cold temperatures and is rare at temperatures warmer than -30o C. At higher latitudes ice fog can occur very quickly and has been known to develop immediately after a plane’s take-off.
Driving any vehicle in low visibilities due to ice fog can be hazardous, therefore speeds should be reduced accordingly.
Rain in the winter can have serious impacts when it falls on an existing snowpack or on frozen ground, as the increased runoff can lead to flooding. When a heavy rainfall is expected that could contribute to localized or downstream flooding and other hazardous conditions, Environment Canada issues a rainfall warning. For some areas of the country, the criteria used for issuing a rainfall warning in the winter is lower than that for a summer rainfall warning.
Although it can snow anywhere in Canada during the winter, the amount of snowfall varies greatly from region to region. It snows less in the North and the interior plains because the air is very dry. Along the west coast of the country, precipitation falls more often as rain, because of the warming effect of the Pacific Ocean. Moving inland though, snowfall increases reaching a maximum of about six metres in the Rocky Mountains. Similar amounts are reported in the Gulf of St. Lawrence due to frequent winter storms, but further inland the winter accumulations of snow drop due to a lack of moisture.
Heavy snowfall can greatly reduce visibility, create hazardous road conditions, and knock down trees and power lines.
Blowing snow is snow driven by wind. It reduces visibility and can cause deep drifts, which can impede transportation and make driving dangerous. Snow drifts can also make it difficult for people to leave their homes or get out of their driveways.
A snow squall is a sudden, moderately heavy snowfall characterized by blowing snow and strong, gusty winds that reduce visibility. Intense but very localized, snow squalls usually last for a relatively short period of time. They often blow in off the Great Lakes, the Gulf of St. Lawrence, and other large bodies of water.
Wind Chill and Cold Temperatures
Wind chill is when the wind makes cold temperatures feel even colder. Environment Canada’s wind chill index will tell you the combined cooling effect of these factors on the human body. It uses temperature-like units to liken the current conditions to how cold your skin would feel on a calm day. Cold temperatures, even if there is little or no wind, can also be hazardous.
Wind chill and cold temperatures can cause exposed skin to freeze very rapidly, leading to frostbite. Extremely cold conditions can cause hypothermia, a potentially fatal condition. Protect yourself by taking steps to stay warm when you are outdoors.
Smog is not just a summertime concern, it can also occur in the winter, often in communities where wood is used for home heating. Winter smog is composed primarily of fine airborne particles, mainly from wood smoke, traffic and road salt. These pollutants can build up in the local area during cold weather, when there is little wind to disperse the particles. This often occurs during temperature inversions and in valleys and other areas that are sheltered from the wind.
Winter smog can be a health hazard, as fine particles can be inhaled deeply into the lungs. Children, the elderly, and people with heart or lung conditions are most at risk. When winter smog occurs in your community, you can help clean the air by not burning wood in your fireplace or woodstove, and by reducing the use of your car.
Check Environment Canada’s Air Quality Health Index to track winter smog in your community and find health information. Use our daily forecasts to plan ahead to protect your health and that of your family.
Winter storms are large-scale weather systems, hundreds of kilometres across, that are called extratropical cyclones because they form and develop outside of the Tropics. These storms gather their energy from the temperature and moisture differences across the boundary where different air masses meet or collide. The larger the differences in the temperature and moisture levels across this boundary, called a front, the more energy there is available for the storms to develop. This is why some are stronger, or more intense, than others.
Winter storms tend to move from west to east and can produce strong winds, heavy snowfall, freezing rain and bitterly cold temperatures as they impact any given area.
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