A ring of wind spinning about 19 miles above the Arctic, far higher than any passenger jet flies, has started breaking apart weeks earlier than ever recorded, and forecasters say the cold it was holding in place could spill into the US and Europe within weeks

Every winter, a vast ring of wind forms high above the North Pole. It circles the Arctic about 19 miles up, roughly three times higher than a passenger jet cruises, and it helps keep the coldest air of the season locked over the far north.

This November, that ring has faltered. Its winds slowed almost to a stop and, around November 10, briefly turned around and blew the other way. Nothing like it has been recorded this early in the season.

The ring of wind above the Arctic

That ring is the stratospheric polar vortex. It sits in the stratosphere, the layer of the atmosphere above where most weather happens. Each autumn, as the Arctic falls into months of darkness, the air above it cools sharply and the vortex strengthens, with winds normally blowing west to east at well over 100 mph.

A strong, steady vortex acts like a fence around the Arctic’s coldest air. When the vortex weakens or splits, that fence can buckle, and lobes of frigid air can push south toward North America, Europe or Asia.

What happened this November

In late October, the vortex’s winds were close to normal. Within days, they collapsed. Measured at a standard height and latitude, they dropped from about 50 mph to about 12 mph in just over a week, then fell to zero and reversed.

That reversal is the official marker of a major sudden stratospheric warming, a rapid heating of the air high above the pole. These events usually happen from mid-winter to early spring. Before this year, the earliest on record were in late November, in 1968 and 2025. This one came weeks earlier than any of them.

How a disruption 19 miles up reaches the ground

What happens in the stratosphere doesn’t affect our weather instantly. Instead, the disruption can slowly work its way downward over two to four weeks, shifting the jet stream, the band of strong winds about 6 to 9 miles up that steers storms.

When the jet stream becomes wavier, cold Arctic air can be pulled much farther south than usual, while milder air pushes north elsewhere. That’s why forecasters are watching late November into December as the period when any effects are most likely to show up at the surface.

What it could mean for the US and Europe

Past events show what’s possible. In 2018, a sudden stratospheric warming in February was followed by the “Beast from the East,” a blast of Siberian air that brought heavy snow and freezing temperatures to Britain and much of Europe.

For North America, forecasters say the greatest chance of colder spells is generally east of the Rockies, including the Midwest and Northeast. But there’s a major complication this year: a very strong El Niño in the Pacific, which tends to bring a milder winter to the northern US. The two are pulling the winter in opposite directions.

Why the outcome is still uncertain

Not every disruption produces severe cold. Some sudden stratospheric warmings barely affect surface weather at all, and the cold that does escape can end up mostly over Asia instead of North America or Europe.

This event is also expected to be brief, with the vortex winds forecast to recover over the coming weeks. That could limit any longer-term impact, though it doesn’t rule out sharp cold snaps in the meantime.

What to watch and how to prepare

Over the next few weeks, look out for updates from NOAA’s Climate Prediction Center in the US and the Met Office in the UK. Their extended forecasts for late November and December will show whether colder air is starting to arrive.

It’s also a good time to prepare for cold weather, whatever happens. Check your heating, insulate exposed pipes, and keep a winter kit in your car with a blanket, scraper, water and a phone charger. If a deep freeze does arrive, check on older neighbors and anyone living alone.