An unprecedented “weakening” in the polar vortex could be bringing snow to the capital earlier than expected this winter.

The phenomenon, which develops each autumn as temperatures plunge in the arctic, is made up of a ring of strong westerly winds situated high in the stratosphere, between 10 and 30 miles above the North Pole.

Held in place by a strong jet stream, it confines the most extreme Arctic conditions to the northernmost parts of the globe - but weather can become unstable if this system weakens or fractures.

When a phenomenon known as Sudden Stratospheric Warming (SSW) occurs, it can shatter the vortex, sending a blast of bitter, freezing air directly towards Europe - and boosting the possibility of snow in the UK.

A major SSW happens when colossal atmospheric waves travel upward from the Earth's surface and crash into the stratosphere, with most such events occurring from mid-winter.

In recent days, the polar vortex has weakened and shifted position, and experts have said that a disruption this early in November is unprecedented in modern observations.

Some forecasts show a reversal of the polar vortex winds by mid-November, which could result in a major SSW event.

The earliest date a major SSW event has been recorded on is November 28, in both 1969 and 2025.

In early 2018, a SSW helped trigger atmospheric changes associated with the Beast from the East, which blasted London with bitter winds and heavy snow.

Jeff Knight, lead climate scientist from the Met Office, told the BBC: "It would appear to be the earliest on record looking back over the 75 years we've been observing, with most experts agreeing this is a very unusual event."

A huge “Godzilla” El Niño unfolding over the Pacific Ocean is also set to cause disruption to worldwide weather patterns, with Knight suggesting it could have "helped load the dice” for a potential SSW event.

Current long-range Met Office forecasts show that the UK should expect a wet and windy start to winter, followed by colder periods in early 2027, consistent with expectations from an El Niño, but an unusually early SSW event was not seen as widely expected.

Freezing and snowy weather is not guaranteed however, with the Arctic not yet as cold as it becomes by mid-winter, and the polar vortex itself having only recently developed.

As such, experts are advising that it is too early to tell whether the weakening in the polar vortex will change the outlook for Londoners this winter.