Canada • Weather

Blizzard Warning

A blizzard warning is a severe weather alert issued in Canada when winds and snow are expected to produce dangerous blowing snow and very poor visibility.

By Ethan Anderson| Reviewed by Olivia Bennett, Standards & Fact-Checking Lead| Updated July 26, 2026|2 min read| Fact-checked

A blizzard warning is a severe weather alert issued in Canada by Environment and Climate Change Canada when winds of 40 km/h or greater are expected to reduce visibility to 400 metres or less from blowing snow for at least four hours (six hours north of the tree line). It warns of dangerous travel and exposure conditions caused by near-zero visibility and strong winds.

Definition

A blizzard warning indicates that blizzard conditions are expected or occurring. The alert is based on wind, visibility, and duration thresholds rather than snowfall amount alone.

Canadian criteria

Environment and Climate Change Canada states that a blizzard warning is issued when winds of 40 km/h or greater are expected to reduce visibility to 400 metres or less because of blowing snow, or blowing snow combined with falling snow, for at least 4 hours. North of the tree line, the duration threshold is 6 hours.

Impacts

Blizzard conditions can make travel difficult or impossible because of near-zero visibility and drifting snow. They can also create exposure risks and contribute to closures, disruptions, and safety concerns.

Blizzard warnings are distinct from other winter alerts such as blowing snow advisories, snowfall warnings, and snow squall warnings. Those alerts may overlap in some storms, but each uses different criteria.

Key facts

A blizzard warning is part of Canada’s public alerting system for hazardous winter weather.
The standard Canadian criterion is winds of 40 km/h or greater causing visibility of 400 metres or less from blowing snow or blowing and falling snow.
In most of Canada, the conditions must be expected for at least 4 hours.
North of the tree line, the same conditions must last at least 6 hours.
They are intended to alert the public to dangerous travel and exposure conditions.

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Canadian context

This is a Canadian public weather alert used nationwide by Environment and Climate Change Canada, with special duration criteria north of the tree line.

Frequently asked questions

What is a blizzard warning in Canada?

It is a weather warning issued when strong winds and snow are expected to create widespread very poor visibility from blowing snow for a sustained period.

Who issues blizzard warnings in Canada?

Environment and Climate Change Canada issues blizzard warnings through the Meteorological Service of Canada.

What are the criteria for a blizzard warning?

The standard criterion is winds of 40 km/h or greater reducing visibility to 400 metres or less from blowing snow, or blowing snow with falling snow, for at least 4 hours.

Are the criteria the same everywhere in Canada?

No. North of the tree line, the same visibility and wind criteria apply, but the duration requirement is 6 hours instead of 4.

Is a blizzard warning based on snowfall amount?

Not primarily. The warning is based on wind-driven visibility loss and duration, although falling snow may contribute.

Why is a blizzard warning important?

It warns of hazardous travel and exposure conditions caused by very low visibility and strong winds.

References

Environment and Climate Change Canada — https://www.ec.gc.ca/meteo-weather/meteo-weather/default.asp?lang=En&n=D9553AB5-1
Supports: Official Canadian blizzard warning criteria, including wind, visibility, and duration thresholds.
Region of Niagara — https://www.niagararegion.ca/emergency/hazards/snowstorm.aspx
Supports: Plain-language description of Canadian blizzard warning criteria and related winter alerts.
Wikipedia — https://en.wikipedia.org/wiki/Blizzard_warning
Supports: General overview noting Canadian regional criteria and the north-of-tree-line duration difference.