Polar vortex collapse begins, colder winter expected in U.S., Canada, and Europe

A sudden stratospheric warming (SSW) event has begun and is weakening the Polar Vortex. This is expected to bring colder winter conditions across the United States, Canada, and Europe.

The latest analysis by Andrej Flis from Severe Weather Europe (SWE) shows that the Polar Vortex has already begun to deform in the mid-stratosphere (around 30 km / 18.5 miles altitude).

This is due to a high-pressure area located over the Arctic Ocean pushing it out of place. This high-pressure area–essentially an “anti-vortex”–is the direct result of the SSW event.

A strong Polar Vortex locks cold air into the polar regions, creating milder winters. But when the Polar Vortex is disrupted or collapses, the cold air can escape, unleashing much colder winter conditions across the mid-latitudes (the U.S., Canada, and Europe).

Peak disruption of the vortex is forecast to occur around Thanksgiving in the stratosphere. However, the effects typically take around 2–3 weeks to propagate downward, meaning weather impacts should become visible across the mid-latitudes by early December.

This is one of the earliest collapse events on record. Only three similar early-season events have occurred in the last 70 years (1958, 1968, and 2000).

Currently, the core of the Polar Vortex is being displaced over eastern Canada and the Northeastern United States. As the vortex collapses, cold Arctic air will begin to spill downward. This positioning creates a “pump” that drives a sustained northerly flow, pulling deep polar air down from the Arctic.

A significant polar outbreak is forecast across the northern, central, and northeastern U.S. Forecasts suggest this pattern will remain fairly stable and increase the probability of a white Christmas across the country. Snowfall from the event is expected to extend far into the southwestern U.S., potentially reaching northwestern Texas.

Because the vortex core is positioned over North America, Europe will likely see a mild, warmer start to the month with westerly and southerly airflows.

Later in the pattern, a high-pressure system may form in the north while low pressure develops to the south, creating an easterly flow. This would open the gates for freezing air to move into Northern and Central Europe–a phenomenon often called “The Beast from the East”–bringing the potential for heavy snow across the region in winter.

References:

¹ Stratospheric Warming Watch: Polar Vortex Collapse has begun, with cold air and snowfall impacts expected – Severe Weather Europe – November 21, 2025

Rishav Kothari

I am an Assistant Editor and Severe Weather & Science Journalist at The Watchers, specializing in real-time severe weather coverage, geophysical event reporting, and research-driven scientific analysis. You can reach me at rishav(at)watchers(.)news.

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