Something unusual is unfolding high above the Arctic: the polar vortex is being disrupted by a sudden stratospheric warming far earlier in the season than usual.

USA Today reports that forecast confidence has risen that the vortex will undergo a major disruption in early November, with meteorologists already seeing it stretch and split into two smaller lobes.

NOAA meteorologist Laura Ciasto told USA Today the event has the potential to be the earliest sudden stratospheric warming since reliable records began in 1958. Stratospheric winds could reverse from westerly to easterly sometime between November 6 and 10, according to Ciasto.

These warming events typically occur between January and March, when the polar vortex is fully developed.

In the records going back to 1958, only two other warming events happened in November, USA Today reports, because the vortex is still growing early in the season and there is less wave energy propagating upward to disturb it.

NBC 5 Chicago notes that if the event meets the criteria for a major sudden stratospheric warming, it could be the earliest documented on record; the previous earliest widely recognized major event occurred around November 28, 1968.

Both outlets stress that the Arctic is unusually warm right now, which limits the cold air available to spill south.

Not necessarily. A disruption of the polar vortex does not automatically mean Arctic air will plunge into the Midwest, NBC 5 Chicago reports; it can take weeks for changes roughly 20 miles overhead to influence surface weather.

USA Today quotes polar vortex expert Judah Cohen of MIT, who says the most certain near-term impact is a period of milder weather across eastern North America, probably through much of November, with any colder effects arriving late November, December, or even January.

Ciasto also points to the very strong El Niño this winter, noting how the two patterns compete will shape what people actually feel at the surface. NOAA's seasonal outlook still favors above-average temperatures across the Great Lakes for December through February.

Sudden stratospheric warmings have produced some of the most memorable cold outbreaks in recent years, but the outcome here is highly uncertain.

According to USA Today, an analysis from AI weather company Brightband suggests this event could be weak and short-lived, settling back toward the pole by late November with little impact on the United States.

Cohen adds that the downward influence is more likely to affect northern Europe or northern Asia than the eastern U.S., and that recent El Niño winters featuring warmings, such as 2023–24, turned out very mild in the eastern states.

For now, a colder spell in late November into December remains possible, and forecasters will be watching closely as the vortex evolves.