Every major single-run weather model now shows the polar vortex weakening toward early November, and the combined forecast puts it at record-weak levels for this time of year, according to Severe Weather Europe , which updates its polar vortex tracking daily.

That doesn’t mean an Arctic outbreak is headed for most of the country next week. But it’s an unusually early shake-up of the system that controls how much frigid air stays bottled up over the North Pole, and forecasters are already looking at what it could mean for December and January.

What the polar vortex actually is

The National Weather Service defines the polar vortex as “a large area of low pressure and cold air surrounding both of the Earth’s poles.” A strong vortex usually keeps the coldest air locked near the Arctic. When it weakens or gets pushed off balance, that air can drop south into the U.S., Canada and Europe.…