Why the U.S. Has Been Home to Earth’s Most Unusually Cold Air This Year
This winter, the polar vortex has taken on an unexpected pattern, making parts of the United States the most unusually cold place on the planet—at least so far this year. Typically, this swirling mass of freezing air stays over northern Canada, Greenland, and the Arctic, keeping the Northern Hemisphere’s coldest conditions locked near the North Pole. However, this year, the vortex has shifted hundreds of miles farther south.
Like the tentacles of an octopus, lobes of the polar vortex have repeatedly reached into southern Canada and the United States, far more frequently than usual. As a result, at least 108 million people in the U.S. have experienced subzero temperatures in 2024, the highest number since 2019. In a remote part of central South Dakota, an area about 50 miles northwest of Pierre has been 11 degrees below average—making it the most unusually cold place on Earth so far this year. This extreme chill is largely due to the region’s proximity to the displaced polar vortex.
Overall, the United States has been the sixth coldest country on the planet this year, a direct consequence of the polar vortex’s unusual behavior. Only five countries—Turkmenistan, Belgium, France, Uzbekistan, and Iran—have experienced colder-than-average conditions on a greater scale. However, these countries are much smaller than the U.S., making it easier for temperature anomalies to stand out.
More than 30 U.S. states have recorded well below-average temperatures, with some areas experiencing drops of more than five degrees below normal. States affected include Washington, Oregon, California, Nevada, Idaho, Montana, Wyoming, Utah, Colorado, New Mexico, Texas, Oklahoma, Kansas, Nebraska, South Dakota, North Dakota, Minnesota, Wisconsin, Michigan, Missouri, Illinois, Indiana, Ohio, Kentucky, Tennessee, Arkansas, Mississippi, Alabama, Georgia, Pennsylvania, Maryland, Virginia, and Washington, D.C. For residents in these areas, bundling up with hats, gloves, and scarves has become a daily necessity.
Despite the extreme cold gripping parts of the U.S., this trend does not reflect a global cooling pattern. In fact, only 12 percent of the planet has been experiencing well below-average temperatures, while 45 percent has seen significantly above-average warmth. Some parts of the U.S., including Alaska, Florida, and Hawaii, have actually recorded above-average temperatures. The five countries with the most unusually warm conditions so far this year are Lithuania, Ukraine, Latvia, Canada, and Paraguay.
So, what’s behind this unusual cold spell? Atmospheric pressure systems have played a major role. A strong high-pressure system has been consistently anchored west of North America and over Alaska, while another powerful high-pressure area has remained over Greenland. These two systems have contributed to above-average temperatures in the Arctic but have also pushed frigid air much farther south into Canada and the U.S.
This shifting pressure pattern has significantly altered the jet stream—a fast-moving river of air that guides storms across the atmosphere. With high-pressure zones acting as atmospheric “stop signs,” the jet stream has taken a more meandering path, particularly near Alaska. As it detoured north into the Arctic Circle, it picked up freezing air and transported it southward, fueling the deep freeze in parts of the U.S.
The unusual placement of these pressure cells and the altered jet stream pattern have also affected the polar vortex, displacing it farther south toward Hudson Bay, Canada. This shift in the troposphere—the lowest layer of the atmosphere—has led to the extreme cold seen across much of the central and northern United States.
While this winter’s pattern has been strikingly cold in some regions, it remains to be seen whether the polar vortex will continue its erratic behavior in the coming months.
The troposphere—the lowest layer of Earth’s atmosphere—is where all weather occurs and where we live. This year, the polar vortex’s behavior in this atmospheric layer has been atypical. However, it doesn’t always behave this way.
In some instances, unusual polar vortex activity begins in the stratosphere—the layer above the troposphere, located four to twelve miles above Earth’s surface. A sudden warming in the stratospheric polar vortex can cause it to destabilize, weakening and wobbling away from the polar region or even splitting into two centers. When this occurs, changes sometimes transfer downward into the troposphere, like paint dripping from one layer to another. This, in turn, affects our weather, bringing intense cold to regions far from the pole.
In early 2025, the stratospheric polar vortex remained mostly normal—strong and anchored from Siberia to Greenland. However, the tropospheric polar vortex behaved very differently. It slid much farther south than usual, frequently impacting the United States with extreme cold. This unusual displacement is what makes this year’s winter outbreak stand out.
Could Climate Change Lead to More Polar Vortex Events?
Scientists continue to study whether significant climatic shifts in the Arctic could lead to more frequent polar vortex episodes in the United States. While research is ongoing, the link between Arctic warming and disruptions in the polar vortex remains an area of active investigation.
The Polar Vortex Gained Attention in 2014
For many Americans, the term “polar vortex” became widely recognized during the brutal winter of early 2014. That year, the Midwest experienced its coldest winter in over 30 years. In Washington, D.C., January 2014 was the coldest month in decades.
Although the term itself gained prominence in 2014, the phenomenon is not new. German meteorologist Richard Scherhag first documented disruptions in the polar vortex in 1952—over 70 years ago.
How Does This Year Compare to the 2014 Cold Spell?
The winter of 2014 was one of the most extreme in recent history. During January and February of that year, 146 million people across more than 40 states experienced subzero temperatures. In contrast, the winter of 2025 has affected 108 million people in just over 35 states—the highest number in six years.
This difference can be partly attributed to rising global temperatures. In 2014, the global temperature was about 1°C above preindustrial levels. In 2024, it was around 1.6°C above preindustrial levels, reflecting the overall warming trend.
U.S. Population Affected by Subzero Temperatures (Millions)
Year People Affected (Millions)
2014 146
2015 138
2016 98
2017 57
2018 116
2019 116
2020 55
2021 93
2022 87
2023 74
2024 83
2025 108
Is This the Last Dance with the Vortex?
Following a week of extreme cold, where temperatures dropped to minus-45°F in Hettinger, North Dakota, a nationwide warm-up is on the horizon. Beginning this weekend, temperatures will surge into the 50s, 60s, 70s, and even 80s across many parts of the country. This shift will temporarily halt the snow and ice storms that have frequently impacted large regions.
However, the polar vortex may not be finished with the United States just yet. Forecast models suggest that another polar vortex event could return in early March. Until then, the vortex will retreat to central Canada—waiting for its next opportunity to strike.
