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A historic atmospheric event has just turned Canada's winter forecast upside down—and it could have major consequences for the weeks ahead.
According to The Weather Network, the stratospheric polar vortex ground to a halt and reversed direction around November 10, 2026, marking a rare and unusually early event.
The polar vortex, the powerful circulation of winds swirling high above the Arctic, has just experienced an unprecedented reversal for November. Instead of strengthening as it normally would at this time of year, its winds have slowed dramatically and actually changed direction.
Read: A rapidly strengthening Super El Niño to reshape Canada's weather this winter
The reversal marks a remarkable development in the atmosphere roughly 30 kilometres above the Arctic. And while Canadians are currently experiencing an unusually mild weather pattern across much of the country, this extraordinary disruption could eventually open the door to a very different start to winter.
According to the report, the timing is particularly unusual because a powerful El Niño would typically favour a stronger polar vortex. Instead, the atmosphere is doing almost the opposite of what historical patterns would suggest.
What does Canada's historic polar vortex reversal mean?
Don't rush to bring out the snow shovels just yet. The effects of a major polar vortex disruption can take weeks to travel down through the atmosphere and influence weather at the surface.
As of November 10, the polar vortex's stratospheric winds had slowed to approximately -0.1 metres per second, indicating that they had reversed direction.
For comparison, typical wind speeds at this time are around 25 metres per second.
That means the current wind speed is just four per cent of normal values, an extraordinary departure from the usual seasonal pattern.
This type of disruption can have consequences far beyond the stratosphere. When the polar vortex weakens or reverses, the effects can gradually work their way down through the atmosphere, influencing the jet stream and encouraging atmospheric blocking patterns.
Those changes can create opportunities for Arctic air to push farther south into parts of North America, however, the process is rarely immediate. Even a dramatic disruption high above the Arctic doesn't guarantee an instant blast of winter weather across Canada.
Check out: A rare super El Niño could be the most powerful in a century
Why Canada is unusually warm despite the polar vortex disruption
While the polar vortex is experiencing a historic reversal, a powerful El Niño and an energized Pacific jet stream are helping maintain unusually warm conditions across much of central Canada.
It's a striking atmospheric contradiction: a major disruption is unfolding high above the Arctic while temperatures across large parts of Canada remain above seasonal averages.
The situation is complicated further by unusually mild temperatures extending deep into Canada's Arctic.
In other words, even if atmospheric conditions become more favourable for Arctic air to move south later this month, there may not be a substantial reservoir of extremely cold air readily available on this side of the pole.
According to the current analysis, some of the coldest air is instead situated on the other side of the Arctic, over Siberia. If that air eventually makes its way towards North America, it could take longer to arrive.
Could Canada see a major winter weather shift in late November?
The final 10 days of November could provide the next important clues. According to the report, European ensemble forecast models are signalling a possible transition of the eastern Pacific oscillation (EPO) into negative territory. This would indicate a significant change in atmospheric circulation over the northeastern Pacific.
Why does that matter?
A negative EPO pattern can favour higher pressure, or ridging, near Alaska and the northeastern Pacific. This can encourage a downstream trough to develop over parts of North America, creating a pathway for colder Arctic air to move farther south.
However, forecasters are still watching to see whether this potential pattern change will become established or whether the current mild conditions will remain dominant.
Will the polar vortex stay reversed?
Despite the historic November disruption, the reversal itself is expected to be relatively short-lived.
Forecast models suggest that stratospheric winds could recover rapidly during the third week of November, climbing back towards and eventually exceeding 25 metres per second.
But a recovering polar vortex doesn't mean the atmospheric disruption is over.
Major stratospheric warming events and polar vortex disturbances can create ripple effects throughout the Northern Hemisphere, influencing atmospheric circulation for weeks after the initial event.
That means the final days of November and the beginning of December could still bring significant changes to the weather pattern, even as the polar vortex itself regains strength.
The big question is whether those changes will be enough to overcome the mild pattern currently dominating much of Canada.
Canada's polar vortex forecast: What happens next?
The coming weeks will be critical in determining whether this historic event translates into a meaningful change in winter weather across Canada.
Here's the timeline meteorologists are watching:
November 10–13: Historic polar vortex disruption, with winds reversing direction.
November 14–20: The polar vortex begins recovering, with stratospheric winds expected to strengthen.
November 20–27: Attention turns to the northeastern Pacific and Alaska. Will atmospheric ridging develop and create a pathway for colder air to move south?
Early December: Meteorologists will be watching to see whether a more persistent blocking pattern develops and whether the broader weather pattern shifts towards winter.
For now, El Niño and the Pacific jet stream appear to have the upper hand. But the extraordinary polar vortex reversal has introduced a new wildcard into Canada's winter forecast. Whether this becomes the beginning of a major pattern change or simply a temporary atmospheric disturbance remains to be seen.
The next big update: The Weather Network's winter forecast is scheduled for release on November 25, offering another look at what Canadians could expect as the season gets underway.
For more information about The Weather Network's report, click here.
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