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Fact Sheet - Winter Weather Warnings

Ontario's infamous winter weather is like the ups and downs and twists and turns of a roller coaster ride

Since most of the province lies on North America's major storm track, winter weather systems travel through Ontario on average every 3 to 5 days. Ontario is the battleground between cold arctic air invading from the north and the warm moist air pushing up from the Gulf of Mexico.

In one day, residents, especially those in Southern Ontario, may be drenched by cold winter rain then covered with snow because north winds have dropped temperatures to well below freezing. As the old saying goes...

"If you don't like the weather, wait a will change!

Ontario winter weather varies day to day and year to year. On Christmas Day in 1980, the people of Toronto shivered in the nose-freezing cold of -25°C. Christmas Day, two years later, Torontonians walked around in sweaters and rain jackets in spring-like 17°C temperatures.

Ontario covers so much territory that the average daily temperatures may differ by as much as 20 Celsius degrees. For example, the average daily temperatures in January range from near minus -24°C in northern portions of the province to a relatively balmy -4°C in Southwestern Ontario.

Not surprisingly, most winters begin earlier and end later in the north than in the south. The winter season in Northern Ontario usually starts in October and ends in mid-May. In Southern Ontario, the winter season starts in November and finishes around the middle of April.

We may joke about winter, but winter weather is no joke. Bitter cold and winter storms kill more than 100 people in Canada every year. That is more than the number of Canadians killed by tornadoes, thunderstorms, lightning, floods, and hurricanes combined.

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Winter Watches and Warnings

When severe weather approaches, Environment Canada warns Canadians in order to give them time to protect themselves, their families and to make sound economic decisions. The Ontario Storm Prediction Centre alerts the public by issuing Special Weather Statements, Winter Storm Watches and Winter Weather Warnings. These are broadcast over regional and local radio and television stations as well as Environment Canada's Weatheradio Network and the Environment Canada weather Web site.

Special Weather Statements

In Ontario, Environment Canada issues Special Weather Statements to flag the approach of significant or severe weather. Special Weather Statements may be issued:

  • To advise you that a weather system of inconvenience is approaching and is 6 to 48 hours away. In this case, Environment Canada does not expect the criteria for a Weather Warning to be reached. But you may be inconvenienced by the weather.


  • To advise you that a storm system with potentially significant impact is approaching and is 48 to 72 hours away. In this case, there is still too much uncertainty to issue a watch or warning but Environment Canada will monitor the development of this storm system which may result in watches or warnings being issued in the future.


  • To advise you that unusual weather is expected. In this case, the Special Weather Statement is issued because of your anticipated interest or concern for safety. Such weather may include the first real snowfall of the season, thick fog over a wide area or thunderstorms in February.


  • To give broader scope to a weather event or express uncertainty. For example, a major winter storm is expected to pass just south of Ontario, and although areas near lake Erie may be brushed by the storm, the worst of it should remain south of the international border.

Weather Summary

  • To summarize the impact from a significant winter weather event.

Winter Storm Watch

Environment Canada issues a Winter Storm Watch as a heads up that severe and possibly dangerous weather is expected soon. The approaching weather may affect your safety or at least be inconvenient.

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Two points to remember about Winter Storm Watches:

  • Winter Storm Watches are usually issued 12 to 48 hours in advance of the approaching bad weather.
  • Winter Storm Watches are an alert to the possibility of severe weather. Please, watch the skies and monitor local radio/television broadcasts or the Environment Canada weather Web site for new developments. Environment Canada will either end the Winter Storm Watch or upgrade it to a Winter Weather Warning, depending on the conditions.
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Winter Weather Warnings

Environment Canada issues Winter Weather Warnings only when severe weather is expected to occur. The weather service issues Warnings 6 to 30 hours in advance of the approaching bad weather. Environment Canada's Warnings are quite specific about the type of weather approaching. Please pay attention to them. There are 11 types of Winter Weather Warnings:

Winter Weather

Blizzard Warning

When forecasters expect all of the following conditions to occur and last for four or more hours:
1. winds of 50 kilometres an hour (km/h) or more
2. visibility of 1 km or less
3. wind chill values of -25 or lower.

Blowing Snow Warning

When blowing snow or blowing snow in combination with falling snow will reduce visibility to less than 1 km for 3 hours or more.

Flash Freeze Warning

When significant ice is expected to form rapidly on road surfaces over much of a region because of a combination of weather conditions. Such conditions typically include temperatures which are expected to fall quickly from above 0°C to well below freezing while precipitation is occurring. This warning is not issued for black ice formation.

Freezing Rain Warning

When moderate to heavy freezing rain is expected,


When light freezing rain or moderate to heavy freezing drizzle is forecast to fall for two or more hours.

Frost Warning

When widespread frost is expected during the growing season.

The criteria for Frost Warnings vary in different parts of the province because the growing season varies significantly across Ontario. Frost Warnings in Ontario are issued:

Rainfall Warning

When 50 millimetres (mm) of rain or more is expected to fall within 12 hours but the ground is dry or covered in snow and is capable of absorbing much of the rain,


When 25 mm of rain or more is expected to fall within 24 hours and the ground is frozen or sodden with little snow on it.

Snowfall Warning

When 15 centimetres (cm) or more of snow is expected to fall within 12 hours.

Snow Squall Warning

When, to the lee of the Great Lakes or other large lakes, snow squalls are expected and

15 cm or more of snow is likely to fall within 12 hours,


the visibility is likely to be near zero for four or more hours, even without warning level accumulations of snow.

Wind Warning

When winds are forecast to reach

60 km/h or more for three or more hours,


wind gust of 90 km/h or more.

Wind Chill Warning

When the wind speed is forecast to be 15 km/h or more and the wind chill values are expected to last for 3 hours or more for the following thresholds:

The criteria for Wind Chill Warnings vary in different parts of the province because people do become acclimatized to winter in their area.

For wind chill values:

-27 to -44 ...risk of frostbite and risk of hypothermia increases with time spent outdoors

-45 or lower flesh may freeze in minutes and there is a serious risk of hypothermia

Winter Storm Warning

When 25 cm of snow or more is expected to fall within 24 hours,


Two or more winter weather warning elements (as listed above) are expected to approach or exceed the criteria. For instance, if 10-15 cm of snow is expected to be accompanied by 2 or more hours of freezing rain.


Other Winter Weather Stuff

"Whiteout" is the term used to describe blizzard-like or blowing snow conditions which reduce visibility to a few metres. People standing in a whiteout are unable to see shadows or landmarks and lose all sense of direction, perception and sometimes even balance as the land and the sky seem to blend into one.

"Sleet" is not a term used by Environment Canada. This term is used in the United States to describe a mixture of rain, snow and ice pellets usually accompanied by biting winds. Environment Canada is wordier and mentions all precipitation types that may occur at the same time.

Blizzards, if we strictly apply the definition, are relatively rare in Ontario!

The "Highs" and "Lows" of Ontario Winters

Highest Recorded Temperature (December to February)
22.2°C at Niagara Falls on Jan. 26, 1950

Lowest Recorded Temperature
-58.3°C at Iroquois Falls on Jan. 23, 1935

Heaviest 24-hour Recorded Snowfall
101.6 cm at Nolalu near Thunder Bay on March 24, 1975

Sunniest Winter (Average)
Thunder Bay

Coldest Wind Chill
Thunder Bay on Jan. 10, 1982. Temperature -36°C with winds at 54 km/h produced a wind chill of -58

Greatest Frequency of Freezing Rain (Average)
Portions of the Ottawa Valley and south and east of North Bay, with 30 to 40 hours of freezing rain, on average, each winter

Snowiest Location
Many locations, mainly near Lake Huron and the eastern end of Lake Superior. Places such as Sault Ste. Marie, Wawa and Wiarton routinely get between 300 and 400 cm of snow each winter.


Obtaining Winter Weather Information

Environment Canada provides winter weather information to the public through local radio and television stations, our Weatheradio network and our weather Web site.

In addition, specific weather information may be obtained directly through an Environment Canada meteorologist via the 1-900 user-pay telephone service Weather-One-on-One 1-900-565-5555. For information on climate and past weather records, you can refer to Environment Canada's climate Web site.

If you require an official past weather report or more information you can call the user-pay
1-900 climate number called ClimateSource at 1-900-565-1111 or send an e-mail to and someone from the Ontario Climate Centre will respond to your request.


Winter Fact Sheet (.pdf version)


part of Environment Canada's Green LaneTM