Polar Vortex Set to Bring Bitter Cold to Eastern US

A shift in the upper atmosphere is about to bring a significant change to winter weather across much of the United States. The polar vortex, a circulation of cold air that normally sits over the Arctic, is becoming more active and will send repeated blasts of bitter cold into the central and eastern regions of the country over the next two weeks.

The cold air will arrive in waves rather than all at once. Temperatures in cities like Chicago and New York are expected to swing dramatically, dropping 10 to 20 degrees below their normal January levels. These temperature swings will be accompanied by lake-effect snow, snow squalls, and flurries stretching from the Midwest to the Northeast.

Background

Much of December brought unusually cold weather to the eastern United States, but that bitter period has largely passed. Warmer air moved in just before Christmas and into early January, giving people in the South and East a break from the extreme cold. The North and Northwest, however, have already been experiencing cooler and wetter conditions that are expected to continue.

The pattern is now shifting again. Very cold air is building up in western and central Canada, and forecasters say it will take some time before that air reaches the central and eastern states. When it does arrive, people across these regions will experience more typical winter cold—and in many cases, colder than what they felt during the past couple of weeks.

Key Details

The Timing and Temperature Swings

Over the next 10 to 14 days, the polar vortex will be particularly active. The jet stream—the river of air that guides weather systems—will develop a large dip centered over the Great Lakes region. This setup will allow cold air to be pushed southward repeatedly.

"Over the next couple of weeks, the jet stream will develop a large buckle with a northward bulge along the Pacific coast and a southward dip centered on the Great Lakes. This setup stretches the polar vortex, sending persistent warmth near the bulge and repeated shots of cold air through the dip."

In Chicago, temperatures are expected to swing from near average to 10 to 20 degrees below average. New York City will see similar fluctuations, ranging from the upper 30s—near the historical average—down to 5 to 10 degrees below normal. These temperature swings will happen over one to two week periods, creating an unstable weather pattern.

Snow and Winter Storms

The cold air will bring multiple rounds of winter precipitation. Clipper systems and lake-effect snow are expected to develop as the cold air moves over the relatively warmer Great Lakes. Snow squalls and flurries will be common from the Midwest to the Northeast.

Storms developing in the southern United States will have difficulty rapidly strengthening along the Atlantic coast and becoming major snowstorms. Instead, most storms will remain weak, move quickly, and exit out to sea during much of next week. However, there are signs that a larger storm system could develop late next week, though meteorologists say it is too early to determine specific details.

Late January Cold Blast

Later this month and into early February, there is potential for a more significant shift in the polar vortex. Some forecasters have identified indicators pointing toward unusual warmth in northern Alaska, a setup that could trigger a major shift in the polar vortex structure.

If this occurs, and depending on snow cover across southern Canada and the Midwest along with ice cover on the Great Lakes, some of the coldest air of the entire winter could arrive. In December, when the Great Lakes were mostly ice-free, temperatures in the Midwest dropped 20 to 30 degrees below average on the coldest days, and the Northeast saw temperatures 10 to 20 degrees below average. Snow and ice cover act as insulators, locking in the cold.

What This Means

For people across the central and eastern United States, the next several weeks will bring a return to more typical winter conditions after the recent warm spell. Those who work outside or rely on vehicles should prepare for fluctuating temperatures and periodic winter precipitation.

The repeated waves of cold air mean that any snow that falls early in this pattern may persist longer than usual, creating hazardous driving conditions. Heating demands will increase significantly, particularly during the coldest periods.

Looking ahead to the broader winter forecast, meteorologists note that the overall winter of 2026 is expected to run slightly warmer than last year's outlook. However, January and February could still bring periods of significant cold, especially if the polar vortex undergoes the major shift that some indicators suggest could occur in late January.