Winters in the United States have gotten warmer in the past 30 years, and some of the coldest parts of the country have warmed up the most.
In Minnesota, winters between 1989 and 2018 were an average of 3 degrees Fahrenheit warmer, compared to a 20th century baseline, according to data from the National Oceanic and Atmospheric Administration analyzed by The New York Times. Florida’s winters were 1.4 degrees warmer, on average, during that time.
Though it might not always feel like it, warmer winters have become more common across most of the country. The most significant temperature increases can be seen in the Northern Great Plains, a region stretching from Montana to Michigan.
The Northern Great Plains have warmed up particularly quickly in part because of the dry winter conditions typical there, said Kenneth Blumenfeld, a senior climatologist at the Minnesota state Climate Office. Cold air moving into the area from Canada and the Arctic is also not as cold as it used to be, he said.
“In Minnesota, we used to get to negative 30 or negative 40 degrees with certain frequency. But no longer. Maybe we’ll now hit negative 30 with the frequency we used to hit negative 40,” Blumenfeld said. But, he added, this difference in cold extremes can be difficult for people to perceive. When it’s that cold out, after all, people tend to stay inside.
The pattern of warming is largely consistent with global trends, said Jake Crouch, a scientist at NOAA’s climate monitoring branch. “In general, northern latitudes are warming faster than southern latitudes. Interior locations are warming faster than coastal locations.”
But there are some distinct regional patterns. In the Southeast, from Louisiana to Alabama and Tennessee, winters saw very little warming between 1989 and 2018, compared to the 20th century average. Scientists have linked this winter “warming hole” to patterns in atmospheric circulation that push colder winter air into the region.
Local trends need to be put in a broader context, Crouch said. The same weather patterns that contribute to an icy cold East Coast, for example, can also bring warmer than average winters to the West Coast and Europe.
We still experience cold snaps across the country, of course. They might even be getting more frequent for the East Coast because of changes in the polar jet stream, a band of high-altitude wind that divides icy Arctic air from the relatively warmer air of the middle latitudes. But, overall, outbreaks of cold air tend to be briefer and warmer than in the past, and they come sandwiched between much balmier winter periods.
Annual national data reveals the extent to which warmer winters (a period defined by NOAA as December through February) have become more common over the past 30 years.
Twenty-three of the past 30 winters were warmer than average for the 20th century, while seven were slightly cooler. Eleven winters were more than 3 degrees above average — a bench mark reached only a few times in the previous 90 years.
Milder winters may sound like welcome news to people who dread bundling up, but they don’t “come in a vacuum,” said Bernadette Woods Placky, a meteorologist at Climate Central. They have ecological and economic consequences, she pointed out, including expanded ranges for pests and allergens, disruption to growing seasons, financial losses for snow-based industries and decreased water availability in the West.