If it feels like cold weather is arriving later than it used to, you’re not imagining it. Global temperatures have been running well above historical averages, and several overlapping climate factors are pushing autumn and winter warmth later into the calendar. The year 2025 ranked as the third-warmest year since records began in 1850, finishing 1.17°C (about 2°F) above the 20th-century average. That extra warmth doesn’t distribute evenly across the year. It tends to show up most noticeably during the transition seasons, when the cold you expect simply doesn’t arrive on schedule.
The Planet Is Holding More Heat
The fundamental reason cold weather keeps getting delayed or diluted is straightforward: there’s more carbon dioxide in the atmosphere than at any point in human history, and it traps heat that would otherwise radiate back into space. This matters most at night and during the cooler months. In summer, the sun is so dominant that a couple of extra degrees can go unnoticed. But in October or November, when temperatures should be dropping sharply after sunset, that trapped heat keeps the air milder than your memory tells you it should be.
This isn’t a subtle shift. November 2025 in North America saw a temperature departure that exceeded 3°C (5.4°F) above the long-term average, making it only the second November on record to hit that mark. It also ranked as the fourth-highest monthly temperature departure for any month in North America’s entire climate history. Canada experienced its fifth-warmest winter on record for December 2024 through February 2025. These aren’t fringe statistics. They represent a pattern where “normal” cold is becoming genuinely unusual.
How the Jet Stream Traps Warm Air
Cold winter weather in North America and Europe depends on the jet stream, a river of fast-moving air high in the atmosphere that acts as a boundary between polar air and warmer air to the south. When the jet stream flows in a relatively straight path, cold air stays bottled up near the poles. When it develops large, slow-moving waves, those waves can dip south and bring brutal cold, but they can also push warm air unusually far north in the peaks between the dips.
Research from Columbia University’s Lamont-Doherty Earth Observatory identified a specific pattern, called a wave-4, where four giant peaks and four matching troughs span the globe and tend to lock in place for weeks. In the troughs, the chance of extreme cold triples. But in the peaks, abnormally warm and dry conditions develop. So depending on where you live relative to one of those peaks, winter can feel like it skipped you entirely, even while another region is getting hammered with arctic blasts. If you’re sitting under a persistent ridge of high pressure (one of those peaks), mild temperatures can park over your area for weeks with no mechanism to push them out.
What La Niña Is Doing Right Now
The tropical Pacific Ocean cycles between El Niño (warmer than average surface waters) and La Niña (cooler than average). These cycles reshape weather patterns across the globe. As of January 2026, La Niña is active, with sea surface temperatures in the key monitoring region running about 0.9°C below normal.
La Niña winters tend to split North America into two zones. NOAA’s official winter outlook for 2025-26 favors above-normal temperatures across much of the East Coast, Southeast, Gulf Coast, Texas, the Southwest, and California. Meanwhile, below-normal temperatures are more likely from the Upper Mississippi Valley and the northern Great Plains westward to parts of the Pacific Northwest. If you’re in the eastern two-thirds of the U.S. and wondering where winter went, La Niña is a big part of the answer. It shifts the jet stream in a way that keeps cold air locked to the north and west, leaving the South and East unusually mild.
NOAA forecasters expect La Niña to fade into neutral conditions sometime between February and April 2026, with about a 60% probability. Once that happens, the strong geographic split in temperatures tends to relax, but by that point, winter is already winding down.
Less Arctic Ice Means Less Cold Air Moving South
The Arctic is losing its ice cover, and that matters for your local weather even if you live thousands of miles from the North Pole. In March 2025, Arctic sea ice hit its seasonal maximum extent at the lowest level in the entire 47-year satellite record. All ten of the smallest winter ice extents have occurred since 2007. Even the ice that does form is thinner and more fragile than it historically was.
When there’s less ice and more open water in the Arctic, the region absorbs more sunlight and stays warmer. A warmer Arctic reduces the temperature contrast between the poles and the mid-latitudes, and that contrast is what drives strong jet stream winds. A weaker temperature contrast can mean a more sluggish, wandering jet stream that’s less effective at delivering sustained cold outbreaks to places like the eastern U.S. or western Europe. The polar vortex, a mass of cold air spinning over the Arctic, is more likely to stay intact and parked up north when the surrounding conditions don’t disrupt it. The result: fewer of those deep-freeze events that used to define January and February.
Cities Feel It Even More
If you live in a city, the warmth you’re noticing is amplified by the built environment around you. Concrete, asphalt, and buildings absorb heat during the day and release it slowly at night, creating what’s known as the urban heat island effect. In New York City, for example, air temperatures in dense neighborhoods like East Harlem have been measured at nearly 5°F hotter than at the relatively open LaGuardia Airport weather station at the same time. Bed-Stuy ran 3.5°F hotter.
This effect is strongest at night and during calm, clear conditions, exactly when you’d expect autumn and winter to feel their coldest. So the baseline warming from climate change gets an extra boost in urban areas, making the absence of cold even more pronounced. If you moved from a rural area to a city, or even from a suburban neighborhood to a denser one, that shift alone could account for part of why winters feel warmer to you now.
Why Some Days Still Feel Cold
None of this means cold weather is gone. It means cold weather is less frequent, shorter in duration, and arrives later in the season than it used to. You’ll still get cold snaps when the jet stream dips south or the polar vortex weakens and spills frigid air into the mid-latitudes. Those events can be intense, sometimes record-breaking, because the contrast between the warm baseline and the invading cold air creates dramatic temperature swings.
What’s changed is the ratio. Where a typical winter in the 1970s or 1980s might have featured several weeks of sustained below-average cold, today’s winters are more likely to feature brief cold intrusions surrounded by long stretches of above-average warmth. October 2025 set a new record as the warmest October ever observed in the Antarctic region, exceeding 1°C above the long-term average for only the second time. When even the poles are running warm, there’s simply less cold air available to export to the rest of the planet.
The short answer to “why isn’t it cold yet” is that the atmosphere is holding more heat, the Arctic has less ice to anchor cold air masses, the jet stream is behaving in ways that favor warmth over large portions of North America, and La Niña is reinforcing that pattern for most of the country. Each of these factors would nudge temperatures upward on its own. Together, they make delayed or diminished cold seasons increasingly common.