What Is Winter Anymore?

What does climate change have to do with winter?

The main thing is that climate change is pushing winter temperatures higher. In fact, the average winter temperature is rising faster than that of any other season. Average temperatures in the lower 48 U.S. states from December through February rose by almost 3 degrees Fahrenheit between 1896 and 2021, compared to 2 degrees in spring and 1.5 degrees in summer and fall, federal data show.

The number of days below freezing each year is also on the decline across the country and across the planet. A decade ago, the U.S. was already seeing two weeks less snow cover, on average, than it did in 1972, according to federal data. And parts of the country, including cities in the Northeast and Northwest, are on track to lose over a month of freezing days by midcentury.

But in many places, daily highs and lows aren’t shifting at the same rate. Winter nights, for instance, are warming even faster than winter days — the total number of freezing nights has been dropping in the U.S. since the 1970s. Colder places are also warming more quickly, with the northern U.S. and especially the Northeast experiencing the most significant rise in average winter temperatures.

That dreary, muddy weather that most of the U.S. saw this past Christmas does, admittedly, happen sometimes for natural reasons. Same with the incessant rain that fell (and then turned to ice) across the Midwest and Northeast in mid-January. With every fraction of a degree the planet warms, however, events like these become more likely — or, at least, that’s what hundreds of the world’s leading climate scientists concluded in the United Nations’ latest synthesis report on the state of the global climate.

If winter is getting warmer, what’s with these bouts of extreme cold the U.S. has been getting?

Some evidence suggests that climate change is actually making cold shocks more likely by destabilizing the polar jet stream, which keeps the frigid air in the far northern hemisphere from moving too far southward (and keeps warm air in the tropics from moving too far northward). As a result, the polar vortex that’s normally confined to the Arctic is liable to stretch south and blast bitterly cold air into the contiguous U.S. That’s what happened in mid-January, when temperatures in Montana and the Dakotas dropped as low as -30 degrees Fahrenheit and the wind chill bottomed out at -60 degrees. Cold air from the same weather system blew all the way to Texas.

That said, this evidence is not rock solid. Whether or not it bears out in the long term, it’s important to remember that a warmer world doesn’t mean it will never be cold.

Recent experience notwithstanding, cold snaps — short periods of abnormally cold weather — are going away, too. Their average duration dropped by six days between 1970 and 2021, a Climate Central analysis found.

A month ago I thought it would never snow again. Now I’m shoveling my driveway for the third time this week. Why are some places suddenly getting even worse snowstorms than usual?

One of the most predictable consequences of climate change is that, as year-round temperatures soar, an increasing share of annual precipitation will fall as rain rather than snow. That’s just what you get when it’s too warm for water vapor to freeze.

One of the less obvious consequences, it turns out, is that a warmer atmosphere holds more moisture, enabling it to dump more precipitation — whether that comes as rain, snow, or wintry mix — during a single storm. As a result, even though climate change is making certain places drier, the biggest winter snowstorms are becoming, well, bigger.

This apparent contradiction had a major impact on the parched West in 2023. Drought is expected to become the norm there as the planet warms, fueling epic wildfires and straining already limited water supplies.

But a string of record snowstorms across the West last winter replenished the region’s dwindling snowpack, feeding mountain streams and helping keep drought conditions at bay (and creating a really good year for ski towns). In California, meanwhile, a barrage of atmospheric rivers drenched lower elevations and broke snowfall records in parts of the Sierra Nevada mountains.

California and its neighbors got off to another rainy (and snowy) start in 2024 — though the recent reprieve from years of severe drought isn’t expected to last.

I’m raising kids in a place that used to get at least a few inches of snow each winter, but lately has hardly been getting any. Will my children know what snow is?

The best answer we can give you today is to say that yes, snow will most likely still exist. But rising generations probably won’t be able to count on snow falling — and sticking — with the regularity it did when you were their age.

Climate scientists don’t have a perfect picture of how quickly the winters we grew up with will give way to a string of months that are rainy, slushy, and unpredictable, but that’s the direction the evidence is pointing. As global temperatures continue to rise, the trends we’ve seen in winter weather over the past couple of decades aren’t expected to reverse course anytime soon.

Are these shifting winter weather patterns impacting other seasons, too?

Many of the ways climate change affects winter are hard to miss. Snow falls later and less often, and when it does come, it doesn’t last as long. That comes with a few perks for the average American — such as fewer frigid winter days — and huge downsides for the communities, ecosystems, and industries that depend on winter being snowy and cold.

The ramifications of warming winters across the U.S. also extend far beyond the end of the season. Accelerated snowmelt causes plants to green and bloom earlier, which can have cascading effects on soil moisture and drought, as well as on the wildlife that depend on these plants for food and habitat. If snowpack fails to accumulate or melts too early, streams will run dry during the hottest months of the year, when animals, plants, and people need them most.

Traditional strains of some fruit crops — like blueberries, cherries and peaches, for example — don’t grow properly in the spring and summer if the preceding winter was too warm. The increasing volatility of winter weather is also affecting the success rate of wintertime crops, especially in the South. By some estimates, the agriculture sector’s biggest companies could lose tens of billions of dollars in value by 2030 because of climate change.

And pests like ticks and mosquitoes are not only expanding northward, they’re also surviving the winter more easily in their historical range, causing their populations to grow and rates of disease transmission to climb.

It’s super warm where I am right now. Is that climate change?

Unfortunately, that’s one question we can’t answer — not for every instance of unseasonably warm temperatures everywhere in the world. What we do know for sure is that warmer average temperatures make unseasonable and extreme weather more likely. So in that sense, yes, odds are very good that climate change is playing a role in that thermometer reading.

But also, events rarely have just one cause. Climate change could be exacerbating a natural weather phenomenon, or you might just have gotten a brief winter reprieve. Whether one sultry February day is “because of climate change” isn’t really the point. The point is that, unless and until we stop emitting greenhouse gases into the atmosphere and start pulling them out, the weather will just keep getting weirder. There is no new normal.