Prairie and Northern Region
Weather Watch and
Weather Warning Criteria

The criteria for watches and warnings are established to meet local and regional needs and may vary slightly from region to region across Canada. The criteria for the Prairie and Northern Region are as follows.

Severe Thunderstorm Watch

Severe Thunderstorm Watches are issued when conditions are favourable for the development of severe thunderstorms with large hail, heavy rain, or damaging wind.

Severe Thunderstorm Warning

Severe Thunderstorm Warnings are issued when a severe thunderstorm has, or will develop and produce one or more of the following conditions:

For Alberta, Saskatchewan, and Manitoba

• Heavy rainfall of 50 mm or more in 1 hour or less.
• Heavy rainfall of 75 mm or more in 3 hours or less.
• Damaging wind and/or gust of 90 km/h or greater.
• Hail with a diameter of 20 mm or larger.
• Waterspout or tornado.

For Northwest Territories and Nunavut

• Heavy rainfall of 25 mm or more in 1 hour or less.
• Damaging wind and/or gust of 90 km/h or greater.
• Hail with a diameter of 12 mm or larger.
• Waterspout, tornado, or funnel cloud.

Tornado Watch

Tornado watches are issued when conditions are favourable for the development of tornadoes.

Tornado Warning

Tornado Warnings are issued when there is a confirmed sighting of a tornado on the ground, when weather spotters report funnel clouds with a rotating thunderstorm, or a tornado signature is detected on doppler radar.

Wind Warning

Wind Warnings are issued when a sustained wind of 60 km/h or greater, or wind gusts of 90 km/h or greater, are expected to last for 1 hour or more. The exception are Alberta's Crowsnest, Cardston, and Lethbridge Regions; where a sustained wind of 70 km/h or greater, or wind gusts of 120 km/h or greater, are expected to last for 1 hour or more.

Dust Storm Warning

Dust Storm warnings are issued when blowing dust caused by strong wind will cause a widespread reduction of visibility to less than 1 km, for 1 hour or more.

Humidex Advisory

Humidex Advisories are not issued as a warning but rather as a Special Weather Statement. It is issued when the Humidex will reach 40 or more with a dew-point temperature of 15°C or higher, and these conditions are expected to last for 1 hour or more.

Heavy Rainfall Warning

Heavy Rainfall Warnings are issued when a rainfall of 50 mm or more is expected in 12 hours or less, or for a rainfall of 80 mm or more in 24 hours or less.

Heavy Snowfall Warning

Heavy Snowfall Warnings are issued when a snowfall accumulation of 10 cm or more is expected in 12 hours or less, or for a snowfall accumulation of 15 cm or more in 24 hours or less.

Freezing Rain Warning

Freezing Rain Warnings are issued when freezing rain is expected to last for 1 hour or more, or there are reports of slippery or hazardous walking or driving conditions due to freezing precipitation.

Frost Warning

Frost warnings are issued when the air temperature is expected to fall below freezing ( 0°C ). Frost warnings are issued for the following:

All Alberta forecast regions except:

• Crowsnest,
• Banff,
• Jasper,
• Kananaskis,
• Nordegg,
• Hinton, and
• Fort Chipewyan.

Only the southern Saskatchewan forecast regions.

• Meadow Lake,
• Prince Albert,
• Nipawin,
• Hudson Bay, and
• south

All southern Manitoba forecast regions except:

• Berens River,
• Poplar River, and
• Grand Rapids.

For northern Manitoba, only for the The Pas forecast region.

Frost warnings are not issued for northern Saskatchewan, Northwest Territories and Nunavut.

click here for a map of forecast regions.

Frost Warnings are issued starting the Saturday of the May long weekend until September 21st; Frost warnings are not issued but the word "frost" is mentioned in the forecast, from September 22nd through to the Thanksgiving Sunday.

Wind Chill Warning

Wind Chill Warnings are issued when wind combined with very cold temperatures will create outdoor conditions hazardous to human activity. Wind Chill Warnings are issued when the following conditions are expected to last for 3 hours or more:

Alberta, Southern Saskatchewan, and Southern Manitoba.

Wind speed of 13 km/h or more and a wind chill of -40 or colder.

Northern Saskatchewan, and Northern Manitoba (except Churchill and York regions).

Wind speed of 13 km/h or more and a wind chill of -45 or colder.

For Churchill and York regions.

Wind speed of 13 km/h or more and a wind chill of -50 or colder.

Northwest Territories (except Holman, Sachs Harbour and Paulatuk regions), and for Qikiqataaluk region of Nunavut.

Wind speed of 15 km/h or more and a wind chill of -50 or colder.

For Holman, Sachs Harbour and Paulatuk regions, and for Nunavut (except for Qikiqataaluk region).

Wind speed of 15 km/h or more and a wind chill of -55 or colder.

Weather Warning

Weather Warnings are issued when any of the following conditions are expected to occur:

• Widespread reduction of visibility to less than ¼ km due to fog, for 1 hour or more.
• Widespread reduction of visibility to less than 1 km due to blowing snow, for 4 hours or more.
• For the first significant snowfall of the winter, 5 cm or more, in areas south of the tree-line and east of the Foothills.
• Blizzard conditions that last less than 4 hours and more than 1 hour.
• When the criteria for two or more of any other warning are met during the course of a weather event.( Except: Winter Storm, Blizzard, Severe Thunderstorm, or Tornado warnings)

Winter Storm Watch

Winter Storm Watches are issued when conditions are favourable for the development of severe winter weather such as: a Blizzard, Heavy Snowfall, Winter Storm, Freezing Rain, or possible future Weather Warning.

For Northwest Territories and Nunavut only, this also includes a possible future Wind Warning.

Winter Storm Warning

Winter Storm Warnings are issued where there is a combination of weather elements that produce the weather related hazard.

For Alberta, Saskatchewan, and Manitoba

Winter Storm Warnings are issued when the criteria for a heavy snowfall warning are expected to be met, plus one or more of the following conditions for 3 hours or more:

• Widespread reduction of visibility to 1 km or less, due to snow and/or blowing snow.
• Wind chills of minus 30 or colder.
• Wind speed of 50 km/h or more.
• Or a report of freezing rain.

Northwest Territories and Nunavut.

Winter Storm Warnings are issued when a snowfall accumulation of 8 cm or more in 24 hours or less is expected, along with at least one of the following conditions for 4 hours or more:

• Wind speed of 40 km/h or more.
• Widespread reduction of visibility to less than 2 km due to snow and/or blowing snow.

Blizzard Warning

Blizzard warnings are issued when all of the following conditions are expected to last 4 hours or more for Alberta, Saskatchewan, and Manitoba, and 6 hours or more for Northwest Territories and Nunavut:

• Temperatures colder than 0°C.
• Widespread reduction of visibility to less than 1 km due to snow and/or blowing snow.
• Sustained wind speeds or gusts of 40 km/h or more.