SNOW and ice warnings cover the length of the UK today amid bitterly cold temperatures.
The chilly snap has brought a blanket of snow to southern England, Wales, Scotland and Northern Ireland.
It has sparked fears of widespread travel delays, with railways, roads and runways impacted.
The Met Office also warned there could be power cuts, but has since withdrawn the alert.
However, warnings for disruption to travel remain current, with cautions that roads and railways will be affected by ice.
Several accidents were reported this morning, with damaged cars spotted on icy surfaces.
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The Met Office warning reads: "Further wintry showers bringing disruption from ice and snow.
"Some roads and railways affected with longer journey times by road, bus and train services
"Some injuries from slips and falls on icy surfaces
"Icy patches on some untreated roads, pavements and cycle paths."
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It had also earlier warned this morning: "Some short-term loss of power and other services is possible, with perhaps a few tree branches down too."
Forecasters expect as much as 8in of snow to fall over higher ground during the "blizzard conditions".
Anyone travelling today should take extra care and check journey times and routes in advance.
Temperatures plunged to a numbing -9.8C in Topcliffe, North Yorkshire, on Tuesday - the coldest morning of the year so far.
Last night was only a fraction warmer at -71.C in Benson, Oxfordshire, according to the latest weather maps.
The Met Office said Loch Glascarnoch in the Scottish Highlands got a 12.5in dumping of snow yesterday, while nearby Altnaharra saw more than 4in.
The wintry conditions pushed the Met Office to issue eight separate yellow warnings for snow and ice today.
These cover most of the UK, and six are in force until tomorrow.
A level three cold weather alert was also issued by the UK Health Security agency and is in place until 9am on Friday.
TRAVEL CHAOS
"Heavy" snow and hail showers will likely bring parts of Britain to a halt, forecasters warn.
Houses in Dore near Sheffield are coated, while Lever Park in Rivington, Lancashire, is covered in white.
And gritters are out over Halkyn Mountain in Lixwm, North Wales, to help reopen some of the many closed roads.
Vehicles and passengers could become stranded, public transport may be delayed or cancelled, and some road surfaces will be dangerous during the "blustery" and "often wintry" showers.
Dozens of schools have been forced to close or open late.
The Met Office has warned temperatures could stay well below average into next week as the wintry spell continues.
Further weather warnings for snow and ice are likely to be issued for later in the week.
SEVEN-DAY COLD SPELL
It comes after dozens of people were injured following a crash involving a double-decker bus in "treacherous" freezing conditions in Somerset.
Met Office meteorologist Tom Morgan said: "If you're planning to make a journey, it's worth leaving extra time for your journey, both to defrost your car and because the roads will be more slippery.
"There will be travel disruption, especially where there is snow."
He added that further alerts are expected to come.
"This is a cold spell lasting around five to seven days so I think by the weekend if you're living in Scotland or Northern Ireland, you will feel it getting a bit milder - but it will remain cold in England and Wales," he continued.
"It may well take until the early part of next week for temperatures to return to normal across England and Wales."
Several police forces and fire services have pleaded with motorists not to travel unless "absolutely essential".
Avon and Somerset Police warned of "extremely icy and dangerous" conditions after it said it had received more than 100 reports of road-related incidents in five hours.
And Cornwall Fire and Rescue Service yesterday said it had seen reports that vehicles had become stuck in snow on the A39 at Trispen and A391 at Bugle.
It tweeted: "Be careful if you're out and about today - snow has fallen in some areas and roads are likely to be icy.
"In built up areas, pedestrians may take to the roads if pavements are dangerous."
There will be travel disruption, especially where there is snow.
Tom Morgan
Elsewhere, Devon and Cornwall Police urged drivers to exercise caution as heavy snow showers sweep across the two counties.
And Essex Police echoed the warning after being called to "a number of collisions" on January 17.
The RAC said there had been a "huge spike" in breakdowns on Tuesday due to icy conditions.
A spokesperson said: "Even though the weather is largely dry in most places, today is proving far busier than yesterday, which is unusual as Monday is generally the biggest day for breakdowns.
"Flat batteries are the top reason for drivers calling us out as cars with older ones finally give up the ghost in the cold.
"Ice, and in some areas snow, are the biggest risks for drivers this week - particularly on stretches of road that haven't been treated.
"It's vital everyone slows down and gives themselves time to plenty of time to brake and react in the event something unexpected happens."
Motorist Jon Terry told how he flipped his car on black ice in Pendoylan, South Wales, while taking his five-year-old son to school.
"I was driving about 15 or 20 miles an hour, pretty slow, and I saw a car up ahead," he said.
"It's a single track lane and you have to give way or reverse to make space.
"The other car was stopped so I put the brakes on and then all of a sudden the back end of my car swung round to the right."
Jon said the front of the car flipped up and it ended up on its side in a hedge.
"Then just all the airbags went off, there was smashed glass all over me and I slid a bit down the road," he added.
On top of the snow and ice, many areas are at risk of severe flooding.
More than 170 alerts and warnings are in force across England and Wales.
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The Environment Agency and local authorities in Somerset have declared a major incident because of flood risk in the county.
The County Councils Network, which represents 36 county and unitary district councils in England, said more than 2,000 warm spaces remain open as temperatures drop and people look for somewhere to keep warm amid the cost-of-living crisis.