Why Is Winter Still So Cold If the Earth Is Warming?

It is the question that surfaces every time a cold snap hits: if the planet is warming, why is it so cold outside? In February 2021, a polar vortex disruption sent Arctic air deep into Texas, knocking out power for nearly 70 percent of the state’s residents and killing at least 210 people. In November 2026, forecasters watched the polar vortex falter earlier than ever observed — the earliest disruption in 75 years of records. Both events happened on a planet that keeps setting heat records.

There is no contradiction here, but the full answer is more interesting than the slogan. A warming planet does not warm evenly, and the unevenness itself can push cold air south. This guide explains the polar vortex, why the Arctic is warming nearly four times faster than the rest of the planet, how that can produce colder winters in some places, and — honestly — where scientists still disagree.

The short answer: weather is not climate

The first part of the answer is the distinction between weather and climate. Weather is what happens over hours and days: a snowstorm, a cold snap, a mild afternoon. Climate is the average of weather over decades. A single freezing week in Texas or London is weather; the planet’s average temperature rising about 1.1°C since pre-industrial times, as assessed by the Intergovernmental Panel on Climate Change (IPCC), is climate.

That distinction alone dissolves the apparent paradox. But it is only half the story, because the warming itself changes how winter weather behaves — and in some regions, that change can mean sharper cold snaps, not just milder winters.

What the polar vortex is

The polar vortex is a vast ring of low-pressure, extremely cold air that circles the North Pole high in the stratosphere, roughly 10 to 30 miles above the ground. It is always there — stronger in winter, weaker in summer — spinning counter-clockwise and holding the coldest air near the pole. NOAA describes it as “a wide expanse of swirling cold air” parked in polar regions, which in winter expands and can send cold air southward.

Below it, at about 5 to 9 miles up, runs the polar jet stream: a fast river of west-to-east wind that acts as the boundary between cold Arctic air and warmer mid-latitude air. When the vortex is strong and stable, it keeps the jet stream flowing in a fairly straight, circular path, and the cold stays locked in the Arctic. When the vortex weakens, stretches or splits, the jet stream loses its shape and starts to meander in deep waves. Cold air spills south through the dips while warm air floods north through the ridges. That is how a disruption tens of thousands of feet above the Arctic becomes a frozen week in Texas, the American Midwest or northern Europe.

It is worth noting that not every cold snap is a polar vortex event. NOAA points out that it takes fairly unusual conditions for the vortex to weaken or migrate far south, and other weather patterns can push Arctic air south too. But when the vortex does break down, the cold outbreaks tend to be the severe ones.

Why the Arctic warms faster than everywhere else

The engine behind all of this is Arctic amplification: the Arctic is warming much faster than the global average. A 2022 study by Rantanen and colleagues, published in Communications Earth & Environment, found that between 1979 and 2021 the Arctic warmed by about 0.73°C per decade, while the globe as a whole warmed by about 0.19°C per decade — nearly four times as fast. NOAA’s Arctic Report Card 2025 puts it more conservatively, saying Arctic temperatures have risen at more than twice the global rate since 2006.

The main reason is a feedback loop built on reflectivity. Snow and ice are bright: snow-covered sea ice reflects up to 90 percent of incoming sunlight, and even bare sea ice reflects 50 to 70 percent. Dark open ocean reflects only about 6 percent. So when warming melts ice and exposes water, the surface flips from reflecting most sunlight to absorbing about 94 percent of it. The water warms, more ice melts, and the loop continues. The same logic applies on land: Arctic June snow cover has fallen by about 13.4 percent per decade since 1967, and the 2025 Arctic Report Card found it is now about half what it was six decades ago. Bare ground absorbs far more sunlight than snow.

Other feedbacks add to the effect: thawing permafrost releases carbon dioxide and methane, warmer Atlantic water is reaching further into the central Arctic Ocean, and the Arctic atmosphere’s stable layering traps warming near the surface. The result is a region warming several times faster than the planet it sits on — and that uneven warming is what disturbs the winds.

How a warmer Arctic can mean colder winters

The jet stream is driven by the temperature difference between the cold Arctic and the warmer mid-latitudes. When the Arctic warms much faster than the tropics, that difference shrinks, and the jet stream loses energy. A weaker jet stream meanders more — it slows down and forms bigger north-south waves that can stall in place, parking cold air over one region for days and warm air over another.

The polar vortex is caught in the same process. A smaller Arctic-to-mid-latitude temperature contrast gives the vortex less energy to hold its tight, circular shape. It becomes more prone to stretching, splitting or being displaced from the pole, and each disruption can send a lobe of Arctic air south. This is the mechanism researchers describe when they say global warming can make winters colder in specific places: not everywhere, not every year, but in particular regions when the circulation lines up that way.

Fresh research sharpened this picture in 2025. A study published in Science Advances in July 2025, led by Laurie Agel with colleagues including Judah Cohen and Jennifer Francis, identified two distinct patterns in the stratospheric polar vortex that steer extreme cold to different parts of the United States — one pushing Arctic air into the Northwest, the other into the Central and Eastern states. The team also found that since 2015, the Northwest has experienced more of these cold outbreaks, tied to a shift in stratospheric behaviour. It is a reminder that “colder winters” is not one uniform trend: where the cold lands depends on the shape of the vortex high above the Arctic.

The Texas freeze: what a disrupted vortex can do

The clearest recent example is Winter Storm Uri in February 2021. A polar vortex disruption sent Arctic air across the central United States and deep into Texas, a state built for heat, not for sustained sub-zero cold. At the storm’s peak, close to 4.5 million homes and businesses lost power, and about 69 percent of Texans lost power at some point between 14 and 20 February. The Texas Comptroller’s office recorded at least 210 deaths, with the state’s health department later putting the official toll at 246, and the Federal Reserve Bank of Dallas estimated the storm’s cost to the state economy at $80 billion to $130 billion.

Uri was an extreme case — a rare alignment of a disrupted vortex, an unprepared power grid and a week of deep cold — but it shows the stakes. The cold did not happen because the planet was cooling. It happened because the machinery that normally keeps Arctic air in the Arctic broke down, and the breakdown itself is connected to how unevenly the planet is warming.

What scientists disagree about

Honesty requires saying that the link between Arctic warming and colder mid-latitude winters is contested. Some researchers, including Jennifer Francis and Judah Cohen, argue that Arctic amplification is already making the jet stream wavier and cold outbreaks more persistent — a 2018 study in Nature linked warmer-than-average Arctic temperatures to cold outbreaks in the eastern United States, and a 2021 study in Science found Arctic warming may increasingly disrupt the polar vortex itself. Other researchers point out that climate models generally project cold extremes to keep decreasing as the planet warms, and that the observational record for the stratosphere only goes back to the 1950s — too short to establish a long-term trend in vortex disruptions. NOAA’s Climate.gov notes that models disagree on whether global warming will weaken or strengthen the vortex.

What is not in dispute: winters on average are getting warmer, and cold snaps have become less frequent and less intense over most land areas since 1950, according to the IPCC. The debate is about whether Arctic amplification is adding a counter-current — more persistent, wavier cold outbreaks in some regions — on top of that warming trend. The Royal Society puts it plainly: global warming tilts the odds in favour of more warm days and fewer cold days, but day-to-day and year-to-year variations will still produce some unusually cold winters. A cold winter, in other words, is evidence about weather, not a verdict on climate.

November 2026: the vortex is faltering right now

This guide is being published in the middle of a live example. In early November 2026, meteorologists observed the polar vortex weakening weeks earlier than ever recorded. Scientists at the European Centre for Medium-Range Weather Forecasts called it, as far as they know, “the earliest stratospheric vortex disruption that has been observed”. Jeff Knight, the Met Office’s lead climate scientist, told the BBC it appeared to be “the earliest on record looking back over the 75 years we’ve been observing”. A major sudden stratospheric warming in November has happened only a handful of times in records going back to the 1950s. NOAA’s Climate Prediction Center issued a rare November disruption alert, noting the effects could persist for up to two months.

Forecasters are careful about what this means on the ground. The Met Office stressed that a major stratospheric warming “does not automatically mean snow or severe cold” for any particular place, and noted that the early timing may limit its severity, since Arctic air is not yet as cold as it will be in mid-winter. The disruption raises the odds of cold outbreaks across the Northern Hemisphere in the coming weeks; it does not guarantee them. That uncertainty is itself the point: a disturbed vortex loads the dice, but local weather still decides where the cold lands.

What to expect from winters ahead

Put the pieces together and the picture is this. Winters, on average, will keep getting warmer as greenhouse gases accumulate, and the total number of cold days will keep falling. But the cold days that do come can still be severe, and in some regions they may arrive in longer, more stubborn spells when the polar vortex falters and the jet stream stalls. The same warming that shortens winter overall can, through the Arctic, make individual winters feel more extreme.

So the next time a cold snap arrives and someone asks how it can be freezing if the Earth is warming, the answer is three sentences: the Earth is warming on average, not everywhere at once; the Arctic is warming fastest of all, and that uneven warming disturbs the winds that keep cold air in place; and when those winds falter, Arctic air escapes south. The cold snap is not proof against global warming. In a warming world, it is one of its stranger symptoms.

Frequently asked questions

Does a cold winter disprove global warming?
No. Global warming is a long-term rise in the planet’s average temperature, measured over decades. A cold week or even a cold winter in one region is weather, and it can happen — sometimes because of the warming itself, through a disrupted polar vortex — while the global average keeps rising.

Will winters keep getting colder?
On average, no: winters are getting warmer and cold snaps less frequent. But individual cold outbreaks can still be intense, and some regions may see more persistent cold spells when the polar vortex is disrupted.

Is the polar vortex new?
No. The vortex has existed as long as records go — the term dates to 1853 — and it disrupts naturally some winters. What is new is the speed of Arctic warming around it, and the question of whether that warming is making disruptions more likely.

Can forecasters predict a polar vortex cold snap?
Partly. Sudden stratospheric warmings can be spotted days to weeks ahead, and their effects on surface weather can linger for up to two months — but exactly where the cold will land remains uncertain until much closer to the event.

For the ocean side of the same warming story, see our guides on ocean acidification and how it affects marine life — the seas are absorbing much of the extra heat, and changing in ways that feed back into the climate.