Forecasters link the dangerous winter cold snap to the stretched polar vortex, moist air masses, and a lack of sea ice.
Warm waters in the Arctic and cold continental land are stretching the notorious polar vortex in such a way that by the end of this week, it will unleash a devastating wave of winter weather across much of the United States. The country is expecting extensive areas of harsh sub-zero temperatures, heavy snowfall, and ice bringing down power lines.
Meteorologists say that the eastern two-thirds of the country are under threat from a winter storm that could rival a major hurricane in destructiveness and partly originates in the Arctic, where warming due to climate change is occurring. They warn that the biting cold is likely to persist until the end of January and early February, meaning that snow and ice will take a long time to melt.
According to forecasts, the storm, which will begin on Friday, will stretch from New Mexico to New England and cover the Deep South. About 230 million people will face temperatures of -7 °C and below, and approximately 150 million, according to the National Weather Service, are likely to be affected by snow and ice; many Americans will experience both.
What Causes the Cold Wave in the U.S.?
The polar vortex, an area of piercingly cold air that usually remains locked in northern Canada and Alaska, is being stretched by a wave in the upper atmosphere that extends from a relatively ice-free part of the Arctic and snow-covered Siberia. As the biting cold sweeps across the U.S., it will encounter moisture coming in from the California coast and the Gulf of Mexico, creating paralyzing icing and snowfall in many areas.
The origins of this system lie in the Arctic, where relatively higher temperatures are fueling the polar vortex and helping to push its cold air southward.
"The atmosphere has aligned in such a way that the pattern of 'warm Arctic, cold continent' seems to have locked in," said Mau. "And it's not just North America: the land from Eastern Europe to Siberia is also exceptionally cold. The entire hemisphere has plunged into deep chill."
Declining Sea Ice Aggravates Extreme Winter Weather
As early as October 2025, changes in the Arctic and low sea ice extent set the stage for such an elongated polar vortex that brings harsh winter weather to the U.S., said winter weather specialist Judah Cohen, a researcher at MIT.
Powerful snowfalls in Siberia have intensified the atmospheric processes that distort the shape of the normally nearly circular airflow. These conditions, he said, have "slightly shifted the odds" in favor of the stretching of the polar vortex.
Cohen co-authored a study published in July 2025 that showed an increase in the number of stretched polar vortex events linked to spikes in harsh winter weather in the central and eastern U.S. over the past decade. According to Cohen, this is partly due to the sharply low sea ice extent in the Barents and Kara Seas helping to trigger a wave pattern that ultimately leads to cold intrusions into the U.S. Warming in the Arctic is causing a more rapid decline of ice in this region compared to other places, as studies have shown.
According to the National Snow and Ice Data Center, Arctic sea ice now has a record low extent for this time of year.
Where Winter Weather Will Hit
The center of the stretched polar vortex will be located somewhere over Duluth, Minnesota, by Friday morning, bringing "long and brutal cold," said Mau. Temperatures in the North and Midwest will drop to nearly record lows, down to -32 to -34 °C, he noted. The average minimum temperature across the continental U.S. will hover around -12 to -11 °C on Saturday, Sunday, and Monday, Mau added.
The two Great Lakes, Erie and Ontario, may freeze over, which will at least slightly reduce the famous lake-effect snowfalls, Mau added.
National Weather Service meteorologist Zach Taylor from the National Weather Prediction Center reported that most areas east of the Rocky Mountains will experience the impact of biting cold, snow, or ice. Treacherous freezing rain may stretch from the southern plains through the central South and into the Carolinas, he said.
"We see the potential for significant icing — enough to cause considerable or widespread power outages or possibly serious tree damage," he said.
And if there is no ice, another significant band of heavy snowfall can be expected, Taylor said. He added that it is too early to predict snowfall amounts, but "significant snow accumulation" is possible "in the Ozark region, in the valleys of Tennessee and Ohio, in the central Appalachians, then in the Mid-Atlantic region and possibly in isolated areas of the Northeast."
