What Is a Cold Wave?
A cold wave is a period of unusually cold weather that lasts long enough to create significant impacts across a region. Temperatures remain well below what is normal for the location and time of year.
Cold waves can last for several days or longer and may affect large geographic areas. The severity of a cold wave depends on how low temperatures fall, how long the cold lasts and whether strong winds produce dangerous wind chills.
Because normal winter temperatures vary considerably across Canada, there is no single temperature that defines a cold wave everywhere. What qualifies as unusually cold depends on the location and season.
Related Conditions
| Condition | Description |
|---|---|
| Cold Snap | A relatively short period when temperatures fall well below normal for a location and time of year. |
| Persistent Cold | Cold weather that remains in place for an extended period with little relief between colder days and nights. |
| Blocking Pattern | An atmospheric pattern that can cause weather systems and cold air masses to remain over the same region for an extended period. |
| Polar Vortex | A large circulation of cold air around the polar regions that can influence periods of unusually cold weather farther south. |
| Arctic Air Mass | A large body of extremely cold air that develops over Arctic regions and can move south into Canada. |
Related Alerts
| Alert | Description |
|---|---|
| Extreme Cold Warning | Warns when very cold temperatures or wind chill create dangerous conditions. |
| Wind Warning | Issued when strong winds are expected to reach warning criteria and create hazardous conditions. |
| Winter Storm Warning | Warns of a significant combination of hazardous winter weather. |
| Blizzard Warning | Warns of strong winds and severely reduced visibility in snow or blowing snow. |
| Snow Squall Warning | Warns of snow squalls that can produce sudden poor visibility and hazardous travel. |
What Causes a Cold Wave?
A cold wave develops when a large area of cold air moves into a region and remains there for an extended period. Atmospheric patterns can prevent milder air from replacing it, allowing temperatures to stay well below normal for several days or longer.
Some cold waves begin when an Arctic air mass moves south from northern Canada or the Arctic. These air masses can bring extremely low temperatures across large areas.
The position of the jet stream can help determine where this cold air travels. Large bends in the jet stream can allow cold northern air to move farther south while other atmospheric patterns can slow the movement of weather systems.
Blocking patterns can make a cold wave last longer. When the larger atmospheric pattern changes very slowly, the cold air can remain over the same region instead of quickly moving away.
Snow cover can also help maintain colder conditions. Snow reflects a large amount of incoming sunlight and can allow the surface to cool efficiently, particularly during clear nights.
A cold wave may produce extreme cold conditions when temperatures become sufficiently dangerous. Strong winds can make the situation worse by producing lower wind chill values.
FAQ
There is no single duration, but a cold wave generally lasts longer than a brief drop in temperature and can continue for several days or longer.
There is no universal temperature. A cold wave is measured relative to the temperatures normally expected for a particular region and time of year.
Yes. If temperatures or wind chills reach dangerous thresholds for the region, an Extreme Cold Warning may be issued.