Temperatures are about to plummet for a significant chunk of the U.S.

A widespread swath of the country, from the northern Rockies to the East Coast, is bracing for a blast of Arctic air that will send temperatures plummeting this week and dropping even further as additional cold air moves in next week.

The air mass, which originated in Siberia, will arrive in the northern Rockies on Monday night, move into the Plains on Tuesday and spread to the East Coast by late Wednesday.

A second, reinforcing shot of cold air will move across the same region from Friday into Saturday before a third moves in next week. The third surge looks to be the most substantial; it is expected to bring temperatures and wind chills possibly reaching low levels not seen for several years, particularly in the Midwest and along the Eastern Seaboard. More than 30 states could experience subzero temperatures during the second week of January. If temperatures reach these levels, high demands for heat and electricity could strain the U.S. electrical grid.

It’s also possible that with the third cold surge, a frigid lobe of the polar vortex, which typically sits near the North Pole, could meander southward into the United States.

While the forecast confidence level for very cold conditions is high, the prospect for widespread snowfall is less certain. Apart from the potential for heavy lake-effect snow later this week, it’s possible but not certain that a winter storm could track from coast to coast over the weekend into next week.

Whether storms generate snowfall may also affect how intense the frigid conditions are.

How cold it could get

As the frigid air mass meanders southward from Siberia, it could drive subzero temperatures in more than 30 states into the second week of January. Single-digit temperatures could reach into the Deep South.

In Washington, D.C., the temperature hasn’t dropped below 5 degrees or zero degrees since 2019. In Philadelphia, the same thresholds have not been breached since 2018 and 1994, respectively.

In Raleigh, North Carolina, the temperature hasn’t dipped below 10 degrees since 2018. In Atlanta, it has happened only three times since 2000.

Some of the unusually cold air may even track through areas of western North Carolina still reeling from Hurricane Helene.

How cold it gets will partially depend on whether there’s snow on the ground. Deep, freshly fallen snow reflects sunlight and traps cold air near the surface, intensifying and prolonging frigid conditions.

While forecast confidence is high that conditions will get cold, exactly how cold it gets depends on a variety of factors, such as snowfall, sky conditions and whether a piece of the polar vortex moves into the country. Those elements will become clearer with time.

Where it might snow

While widespread cold is a near certainty, widespread snow is not a sure thing.

In the Great Lakes, however, the chances for another heavy lake-effect snow event are rising, starting Wednesday or Thursday. Early indications are that the heaviest accumulations will occur in the snow belts east of Lakes Ontario and Erie, such as near the Tug Hill Plateau and south of Buffalo.

From this weekend into early next week, a winter storm may track from coast to coast, bringing hazardous weather from the Northwest to the Northeast – and many places in between. The storm could bring accumulating snow to the Plains and Midwest over the weekend.

However, there’s a chance the Siberian air mass could be so cold and dry that it suppresses storm activity to the south.

Though the forecast is uncertain, another winter storm could form near the East Coast later next week, around Jan. 9 or 10.

The jet stream, a ribbon of fast-moving air in the upper atmosphere, is forecast to dip down over the eastern states, setting the stage for cold and stormy conditions.

How long the cold will last

This frigid weather pattern could remain for the first two to three weeks of January.

During this time, while colder temperatures persist in much of the East, the West is forecast to generally be milder than average, as is Alaska.

But the most unusually cold air may shift toward the Pacific Northwest during the late part of January, with more seasonable temperatures returning to the central and eastern states.

Scarves, hats and gloves will be essential accessories for millions of people across the U.S. in the weeks ahead as forecasters remain on polar vortex watch.