Britons could be hit by colder temperatures later this month as a weakening polar vortex threatens to bring Arctic air.

The polar vortex is a ring of powerful winds that helps keep freezing air near the North Pole.

If it weakens, it could allow colder Arctic air to sweep south towards Britain, increasing the risk of wintry weather.

Met Office forecaster Marco Petagna said: “At the moment, we’ve got a warming taking place in the stratosphere.

“The polar vortex in the stratosphere is starting to weaken.”

Mr Petagna added that if winds reverse direction, it would become a “major sudden stratospheric warming” event — potentially the earliest ever recorded.

The forecaster said: “For the UK, it does increase the chance of cold weather, normally a few weeks down the line, so sort of deeper into November is when we’re more likely to see an influence if it does happen.

“It’s important to emphasise that there was a major warming event last November, and on that occasion it didn’t directly lead to much cold weather in the UK.

“It doesn’t always happen, it just increases the chance of it occurring.”

Forecasters will monitor the polar vortex over the next few weeks to see whether the disruption could bring colder conditions to Britain.

Meanwhile, a yellow fog warning is in place across parts of the South West, South East and Midlands on Sunday morning, potentially disrupting travel for those heading to Remembrance services.

Visibility could plunge below 50 metres in places, with fog slow to clear in the morning.

Mr Petagna said conditions should improve through the day, with sunshine breaking through, gentle winds and temperatures around 9C or 10C.

Monday is expected to bring another foggy start before rain and stronger winds spread across the UK on Tuesday and Wednesday.

There is also a chance of wintry showers over higher ground in Scotland on Thursday and Friday.