A brutally cold air mass is coming. How chilly will it get in your region?

The weirdly warm November weather will soon come to a crashing end, thanks to an air mass moving from the Laptev Sea north of Russia — over 4,000 miles away from the U.S. East Coast, where its journey will end this weekend.

It may seem like an uninvited postholiday guest. But when much of the eastern two-thirds of the United States has been 5 to 10 degrees warmer than average this month, it may be greeted with arms wide-open. And this polar plunge has no intention of departing any time soon.

It’s expected to stick around into mid-December, sparing no state east of the Rocky Mountains from an unusual chill, to varying degrees.

The animation below shows the progression of temperatures in the lower atmosphere, as a difference from average temperatures from late November into mid-December.

What this unusual chill means for you

Areas from Minot, North Dakota, to Miami will soon experience their coldest weather of the season so far.

That’s not saying much, given that the calendar will soon turn from November to December, but the temperature contrast from early to mid-November will be stark. Consider that Minot, which had a high temperature of 67 degrees earlier this month, will struggle to get above zero degrees for a high on Friday after an overnight low of around minus-15 degrees. The average high this time of the year is in the mid-30s.

While these temperatures are undeniably cold, record lows in this part of the country generally range from minus-20 to minus-30 degrees in late November. In other words, the incoming air mass is unusually cold but not record-breaking.

After a long, hot summer and fall, Floridians can look forward to nighttime temperatures in the 30s, 40s and 50s.

The effect of the polar plunge on your neighborhood will be relative to your local climate, but it will be felt by all.

The map below shows the coldest forecast temperature from a leading global weather model from Thursday to Dec. 11.

More than two dozen states may experience temperatures in the single digits or lower, generally across the northern tier, covering a population of around 43 million.

Temperatures in the teens could reach as far south as Alabama and Georgia, while northern Florida could reach the 20s.

No state is forecast to be spared from freezing temperatures.

Suffice it to say, if you live in the central or eastern United States, your December heating bill is likely to be higher than normal. And if it’s wood that you use to heat your home, make sure you have a pile that will last.

So dust off the puffy jackets, hats and gloves — they will come in handy in the weeks ahead.

As the frigid air flows over the record warm waters of the Great Lakes, conditions will become ripe for heavy lake-effect snow. Lakes Ontario, Erie, Huron, Michigan and Superior are all reporting their warmest conditions on record for the time of year. The greater the temperature difference between the lake and the air about one mile above the ground, the more vigorous the localized snow bands can become, fueled by extra instability.

Lake-effect snow will start in earnest late Thursday and fall heavily at times into next week, with total accumulation probably measured in feet in some areas. Winter storm watches have been issued for areas downwind of Lakes Ontario and Erie.

The map below provides an indication of where the heaviest snow will fall over the next week.

The anatomy of a polar plunge

In order for it to get really cold, the air has to come from a really cold place. A polar region, such as north of Russia, fits the bill.

But there’s more to it.

Not all polar plunges are created equally. Some come with a special characteristic called “cross polar flow.”

Cross polar flow can occur when air pressure patterns at high latitudes, such as around Alaska, Russia and Greenland, align to allow air from one side of the polar region to track, unabated, to another side.

This can be thought of as an polar air gateway. When the gates are open, the air mass has an opening to dive deeper into parts of the hemisphere that it typically wouldn’t reach — an open field, so to speak, without anything there to tackle it before reaching the end zone.

In this case, the end zone is the central and eastern United States.

While the widespread and persistent nature of colder-than-average temperatures is notable for the central and eastern states, the western states are expected to revert into a milder, drier pattern.

Why it matters

Just as one heat wave isn’t proof of climate change, a single cold spell isn’t a sign that the long-term warming trend has been reversed, nor that the 2024-25 winter season will necessarily be colder and snowier than average.

The 2023-24 winter season ranked as the warmest winter on record for the contiguous United States. The last time the country had a colder-than-average winter was in 2013-14.

While the trend toward milder winter temperatures is unmistakable, unusually cold weather still happens in a warming world, though it’s often the exception, not the rule.

In October 2024, monthly average temperatures in the upper 10 percent of historical observations covered 45% of the planet, while less than 1% of the planet experienced temperatures in the lowest 10 percent.

And despite El Niño’s demise this year and the rise of a possible La Nina event, which tends to cool the planet, 2024 is highly likely to become the warmest year on record.

Long-range guidance shows the unseasonably cold weather pattern easing later in the month.