Polar Vortex UK Explained: Snow Risk, the Weeks-Long Lag and the Winter Outlook

The early disruption to the polar vortex does not mean snow is on the way: the Met Office said on 4 November that, for now, it is “not a forecast of an impending UK cold spell”, and the only wintry weather in its long-range forecast is “a few wintry showers” in the far north. The Met Office calls the disturbance high above the Arctic exceptional for this early in the season. It says a sudden stratospheric warming (SSW) raises the chance of colder UK weather without guaranteeing it, and that any surface effect can take two to six weeks to arrive. Its long-range forecast, issued at 13:00 UTC on Saturday 7 November, says temperatures will probably be above average overall from 12 to 21 November, after a cold start, and are likely to be above normal overall from 21 November to 5 December. As of 13:20 UTC on Saturday 7 November 2026, the Met Office had not confirmed that a major sudden stratospheric warming, meaning a reversal of the vortex winds, has happened.

What is the polar vortex?

The polar vortex in these headlines is a ring of strong westerly winds about 10 to 50km up in the stratosphere, circling a pool of very cold air over the Arctic in winter, according to the Met Office. It forms each autumn as the stratosphere above the North Pole cools with the loss of sunlight. It sits far above the weather we feel, but changes in its strength and shape can influence the jet stream below.

The Met Office describes what usually happens in two broad states:

• A strong, stable vortex tends to support a strong, fairly straight Atlantic jet stream. For the UK that often means milder, wetter and windier weather steered in from the west.
• A weakened or disrupted vortex can go with a weaker, more meandering jet stream. That raises the chance of colder air moving south out of the Arctic, or of high pressure settling in places that block the usual westerly pattern.

The Met Office’s own summary describes the vortex as a background driver that can make certain patterns more likely, rather than a switch that turns cold weather on or off.

What is a sudden stratospheric warming?

A sudden stratospheric warming (SSW) is a rapid rise in temperature high over the pole, of up to about 50C in a couple of days, that comes with a sharp weakening of the vortex winds, according to the Met Office. It happens between 10km and 50km up, so nobody on the ground feels the warming itself.

The Met Office explains the stages like this:

• The trigger: large atmospheric waves in the lower atmosphere travel upwards and disturb the vortex. They can stretch it, push it off the pole or, in some cases, split it.
• The warming: as the vortex winds weaken, air over the pole sinks and is compressed, which is what makes the stratosphere warm so quickly.
• A major SSW: the westerly winds in the mid-stratosphere reverse and become easterly. The vortex may be displaced away from the pole or split into two smaller vortices.
• The aftermath: it can take several weeks for the vortex to recover, and the effects can work down towards the surface during that time.

SSWs are not annual events. The Met Office says they do not happen every year, and the University of Reading’s Professor Andrew Charlton-Perez puts them at about once every two years.

What is happening to the polar vortex right now?

The vortex is being disturbed unusually early and a warming is under way, but the Met Office had not confirmed a major SSW as of 13:20 UTC on Saturday 7 November 2026. Its Deep Dive, published at 14:33 UK time on Wednesday 4 November, set out the position:

• Stretched already: the vortex was unusually stretched by what forecasters call wave two activity, where two large atmospheric waves push into it from opposite directions. That activity was considerably stronger than average for the time of year.
• Moving off the pole: forecasts suggested the vortex would become increasingly displaced from the North Pole.
• A possible reversal: many members of the European ECMWF model’s ensemble suggested the winds could briefly reverse during the coming week, potentially meeting the definition of a major SSW.
• Not certain: the Met Office said the expected reversal was relatively weak and short-lived, and that there remained uncertainty over whether a major SSW would occur.

The most recent Met Office comment came on Saturday 7 November, in a PA news agency story published at 12:32 UTC. Met Office forecaster Marco Petagna told PA: “At the moment, we’ve got a warming taking place in the stratosphere.” He said the vortex was starting to weaken, and PA reported that he said it would become a major SSW if the winds reverse. That still treats the reversal as something that has not yet been confirmed. The Met Office blog and press centre, read between 13:15 and 13:20 UTC that day, had no vortex update after the explainer of 5 November.

Many headlines call this a record, but the Met Office’s own posts do not use that word for the vortex event, saying exceptional and exceptionally early instead. The BBC reported on 6 November that the Met Office’s Jeff Knight said it “would appear to be the earliest on record”. Prof Charlton-Perez says the best records go back to 1979, when satellite observations began, with reasonable records back to the 1940s, and that in all that time no SSW has come earlier than very late November.

As for why, the Met Office points to an intriguing connection with the exceptional El Niño in the Pacific, which can strengthen the waves that disturb the vortex. Prof Charlton-Perez says it is too early to say whether El Niño is the cause without more analysis.

Why could it take weeks to reach the UK?

Because the change has to work its way down from the stratosphere to the lower atmosphere, which the Met Office says can take two to six weeks after an SSW. Its standing explainer puts it more loosely: the effect on surface weather usually takes a few weeks, or into the next month.

The Met Office describes the chain like this. The reversed, easterly winds high up gradually work downwards. Lower down, that can weaken the Atlantic jet stream and make blocking high pressure more likely. It is the blocking, not the stratosphere itself, that changes the air reaching the UK.

Two things follow from that:

• The lag is a window, not a date. The Met Office has not said when, or whether, any effect will reach the UK this time. Mr Petagna told PA that any influence was more likely “deeper into November… if it does happen”. The Met Office’s own long-range text, issued at 13:00 UTC that day, still has temperatures probably above average overall through that period. BBC Weather’s Monthly Outlook, updated at 15:43 UTC on 6 November, mentions a possible colder spell in early December, says it has particularly low confidence, and says it partly depends on how the atmosphere responds to the vortex disturbance.
• Next week’s chilly start is not tied to the vortex in the Met Office text. The long-range forecast describes a cold start to the 12 to 21 November period without linking it to the vortex, and it falls before the two-to-six-week window the Met Office describes. For what next week looks like, see whether the UK is in for a cold snap in November .

Does a sudden stratospheric warming mean snow in the UK?

Not automatically: the Met Office says an SSW “does not automatically mean snow or severe cold for the UK” and that, historically, it raises the chance of colder weather while the outcome is far from guaranteed. The Met Office’s explainer adds that an SSW most often leads to cold, dry conditions, and that wintry showers depend on temperatures and moisture.

Where blocking high pressure sets up matters most. The Met Office’s Deep Dive gives three cases:

• High pressure over the UK: quieter, drier weather with more frost and fog.
• Blocking further north: easterly winds become more likely. The Met Office’s explainer says easterlies tend to bring colder, drier air and can produce sleet or snow showers, especially in eastern areas.
• High pressure to the west: northerly winds become more likely, which can bring wintry showers, ice or snow depending on temperatures and moisture.

The Met Office also says some SSWs are followed by notable cold spells while others have little lasting effect on UK weather, and that the strongest impacts sometimes land elsewhere in Europe. A Met Office blog from November 2025 said SSWs do not always bring cold, but “a cold snap follows more often than not”. Mr Petagna offered a recent counterexample to PA: he said there was a major warming event last November, and that on that occasion it did not directly lead to much cold weather in the UK.

Timing works against snow this time. The Met Office says there is generally less cold air available across the Northern Hemisphere this early than later in winter. The BBC’s Monthly Outlook says there is “not yet a reservoir of notably cold air” to tap into. Prof Charlton-Perez, in a University of Reading comment dated 6 November, said: “snow now in the UK is unlikely, and the forecasts don’t currently suggest it”. He said too much heat is left over from summer in the oceans, land and atmosphere, and that the link between an SSW and snow would be stronger later in winter.

Could it bring a dry spell instead?

It could, and the University of Reading’s Prof Charlton-Perez suggests that may be the bigger concern, although no dry spell is in the Met Office forecast yet. He says an SSW normally means the UK is, on average, colder and drier, with more settled conditions. The Met Office’s explainer likewise says an SSW most often leads to cold, dry conditions, depending on how the whole atmosphere responds.

His point is about water. He says some parts of the UK are still in drought or severe drought after a dry, warm summer, and need more than 120% of usual rainfall every month over the winter to recover. If this event or later SSWs bring long dry spells, he says reservoirs may not refill over winter, with knock-on effects for water supplies next summer.

That is a conditional warning, not a forecast. For now, the Met Office long-range text issued at 13:00 UTC on 7 November has changeable, at times wet weather through late November, with conditions possibly turning drier overall into early December. The Met Office’s three-month Outlook also notes that there remain risks to drought recovery.

Did an SSW cause the Beast from the East?

The Met Office connects the cold, snowy spells of 2009-10, 2013 and the 2018 Beast from the East to the surface effects of SSWs. Its explainer says a more snaking jet stream can build high pressure over the North Atlantic and Scandinavia, with cold easterly winds on its edge. In some cases the drop in temperature brings snow, which it says is what happened in early 2018.

All three came later in the season than this one. The Met Office stresses that SSWs do not always affect UK weather, and with no comparable event this early, Prof Charlton-Perez told the BBC it is harder to anticipate a cold spell.

What does the Met Office long-range forecast say?

As of the issue stamped 13:00 UTC on Saturday 7 November, the Met Office says temperatures will probably be above average overall from 12 to 21 November and are likely to be above normal overall from 21 November to 5 December, with “a few wintry showers” likely in the far north at the start. It was the latest issue at 13:23 UTC on Saturday 7 November, so a newer issue may since have replaced it. The text is updated daily, written for the UK as a whole, and drawn from a range of models.

In summary:

• Thursday 12 to Saturday 21 November: rain in the south clears as clearer conditions spread from the north. A few wintry showers are likely in the far north, but otherwise a spell of fine, dry weather develops for most towards the weekend of 14 and 15 November. Over the following week, a change to more changeable weather is likely, with Atlantic weather systems bringing rain and some strong winds. In the Met Office’s words: “After a cold start, temperatures will probably be above average overall.”
• Saturday 21 November to Saturday 5 December: changeable or unsettled, with heavy rain at times and a chance of strong winds, and drier, brighter interludes between systems. Conditions could possibly turn drier overall into early December. Temperatures are “likely to be above normal overall”.

Neither block mentions the polar vortex.

What is the Met Office winter outlook?

The only official seasonal product out now is the Met Office’s 3-month Outlook for November to January, and it was issued on 26 October, before anyone was talking about the vortex. It names El Niño and the warming climate as its drivers and does not mention the polar vortex or an SSW. The first seasonal issue written after the disruption, covering December to February, is due on 30 November.

In its temperature figures, which are averages across the three months and the UK land area rather than a forecast for any day, the Met Office gives:

• Cold: a 15% chance, against a normal 20%
• Near average: 55%, against a normal 60%
• Mild: 30%, against a normal 20%

So the starting point before the vortex news leaned mild, though the Outlook does not rule out cold spells, and it says cold impacts remain possible later in the period. Whether the December to February issue shifts those probabilities is the thing to look for on 30 November. On rain, the same Outlook makes a wet season twice as likely as normal, yet still flags risks to drought recovery, which is where Prof Charlton-Perez’s dry-spell warning fits in. For the El Niño background, see what the record El Niño signals for UK winter .

Why do headlines talk about a collapse and snow bombs?

Because media wording runs ahead of the Met Office’s. Some national headlines describe a polar vortex collapse. The Met Office’s posts use disturbed, disrupted and exceptional, and describe a possible weak and short-lived reversal, not a collapse.

Snow-map stories are a separate thing. These stories, including a Daily Express story of 6 November about snow in Scotland on 15 November, credit their maps to WXCharts. They are not Met Office forecasts.

Are any weather warnings in force?

The only Met Office warning, as read at 13:20 UTC on Saturday 7 November, was a Yellow warning for fog from 00:00 to 10:00 UTC on Sunday 8 November. The Met Office says dense fog could cut visibility to less than 50 metres in places, and be slowest to clear across parts of the West Country and central southern England. There were no snow or ice warnings.

Warnings can be issued or changed at short notice, so check the Met Office warnings page directly before travelling.

When will the picture be clearer?

Over the next few weeks, in stages, and no single date settles it. The things to watch:

• Whether the reversal happens: the Met Office said on 4 November that it would be watching the vortex closely and whether changes work their way down.
• The long-range forecast: updated daily on the Met Office site.
• BBC Weather’s Monthly Outlook: its next update is on Tuesday 10 November, which it says will look for clearer signs of a possible colder turn by early December.
• The December to February Outlook: due from the Met Office on 30 November, the first seasonal issue written after the vortex disruption.

Sources

• Met Office: Deep Dive, could changes high above the Arctic influence the UK’s weather? (4 November 2026)
• Met Office: what is the stratospheric polar vortex and how does it affect UK weather? (5 November 2026)
• Met Office: sudden stratospheric warming explainer
• Met Office: what is sudden stratospheric warming? (November 2025)
• Met Office: UK forecast and long-range forecast
• Met Office: UK 3-month Outlook, November 2026 to January 2027 (PDF)
• Met Office: UK weather warnings
• Met Office: official blog
• University of Reading: expert comment on the early polar vortex split (6 November 2026)
• PA via Chelmsford Weekly News: UK faces increased risk of cold snap as polar vortex weakens (7 November 2026)
• BBC Weather: could the earliest weakening of the polar vortex on record bring UK snow? (6 November 2026)
• BBC Weather: Monthly Outlook
• Daily Express: WXCharts snow-map story (6 November 2026)