Time for your winter woolies: Snow warnings are issued across the UK as polar vortex plunges the country into its coldest winter for five years 

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Britons were warned today to expect the coldest winter for five years with six inches of snow set to fall this week. 

The Met Office has forecast the highest risk of a cold start to the winter since the bitter season of 2010/11.

The usual probability of a colder than average start to winter is 20 per cent, but it stands at 30 per cent this year.

A key reason for colder temperatures are the 'disturbed' polar vortex Arctic winds affecting the Atlantic jet stream.

And the La Nina atmospheric phenomenon, the opposite of El Nino, is bringing lower temperatures in the tropics. 

A motorist travels along the snow-lined B6277 near Garrigill in Cumbria this morning following a weekend of snow showers

A snow-covered sign is seen next to the B6277 in Upper Teesdale, County Durham, this morning ahead of a bitterly cold week

Whitby's all weather lifeboat was launched this morning in rough conditions so a crew member could qualify as coxswain

The lifeboat crew must prove they can steer the boat in and out through the narrow pier at Whitby in North Yorkshire

Today, bright weather and temperatures between 5C (41F) and 8C (46F) are forecast for much of the country.

But colder weather will move in overnight causing widespread frost and large amounts of snow in parts. 

Forecasters said 6in (15cm) could fall above 1,000ft in northern England and Scotland, and 3in (8cm) above 650ft.

They also believe snow could settle to low levels over parts of Yorkshire and the Midlands from tomorrow night.

The Met Office has warned of tricky driving conditions when a band of rain turns to snow as it encounters cold air.

It follows a chilly night that saw temperatures fall to -5.3C (22F) at Katesbridge in County Down, Northern Ireland.  

POLAR VORTEX: THE NAME FOR 100MPH WINDS CIRCLING THE ARCTIC

Polar vortexes happen seasonally at the North Pole with polar winds circling the Arctic at more than 100mph.

The winds blow in an anti-clockwise direction in the stratosphere above the Arctic, trapping cold air.

The vortex can move into Siberia and North America when high-pressure systems push up and split it into two.

This also causes the North Atlantic jet stream to buckle and move south, causing a freeze in Europe and the US.

The vortex hit the US hardest in 2014, affecting 200 million people and causing billions of pounds of damages.

For more than 30 years, the polar vortex has been weakening because of the sea ice loss in the Arctic.

Commuters faced delays today after a train struck a tree which had fallen in high winds at 6am near Ashford, Kent.

The train was not damaged following the fall at Beechbrook Farm and there were no reported injuries

But the line was closed for about 50 minutes as engineers removed the tree from the track and cleared debris.

Emma Sharples, forecaster for the Met Office, said Britain would wake up to ‘frosty scenes’ tomorrow.

She added that Scotland will see the first ‘fairly significant snow’ of the year and many places will be sub-zero.

Ms Sharples said: ‘Even towns and cities will probably be just about hovering between 0C (32F) and 1C (34F).’

The Met Office said 6in (15cm) of snow could fall above 1,000ft in northern England and Scotland, and 3in (8cm) above 650ft

Today's forecast: This afternoon will be sunny for most, but showers continue along North Sea coasts and South West Wales

Overnight lows: Tonight is going to be chilly again, with temperatures of -5C possible for the second night in a row

But wet and windy weather is forecast for Friday and Saturday and temperatures of 10C (50F) to 14C (57F).

‘We will see a slight change as we go towards the end of the week,’ Ms Sharples said.

‘Less cold than it is at the moment, but probably still a little bit below average for the time of the year.’ 

The temperature drop follows the second mildest September on record and October being the driest for 65 years.

Parts of northern England woke up to a dusting of snow yesterday as the first cold snap of the season arrived.

Temperatures fell to -2C (28F) in Wisley, Surrey, and -1C (30F) in Bournemouth and London on Saturday evening.

Mountaineer Alan Hinkes braves the winter conditions on Swirrell Edge on the Helvellyn range in the Lake District yesterday

Heavy snow over northern England caused chaos for motorists yesterday, especially in the Cumbrian village of Alston

Clear skies and brisk northerly winds made Bonfire Night feel decidedly chilly during what was a chilly weekend.

And communities in Cumbria and parts of the Northern Pennines saw the first snow flurries descend yesterday.

Drivers on the A689 in Nenthead, Cumbria, were left stranded as heavy snow hit the remote village.

While the snow ploughs got to work clearing roads, children took to the slopes to make the most of sledging. 

Other parts of Cumbria, County Durham, the Yorkshire Dales, Northumberland and Scotland also had some snow.

Going for a stroll: Alston in Cumbria suffered snow showers yesterday, as forecasters said up to six inches could fall this week

Mountaineer Alan Hinkes goes over Swirrell Edge in the Lake District yesterday as snow sweeps across northern England

Gareth Harvey, forecaster with MeteoGroup, said: ‘It’s the first really chilly snap for this autumn.

‘Temperatures are a little below where they should be for the start of November.

‘It’s nothing exceptional but people will feel it because we’ve been used to mild weather thus far.’ 

British Gas is expecting 254,000 calls reporting boiler breakdowns or problems with home appliances this week. 

Normal service appears to have resumed at the start of November after weeks of unseasonably warm weather. 

It comes after temperatures reached 22.2C (71F) at Trawscoed in West Wales only a week ago on Halloween.