THE Met Office is warning of blizzards with a 4-day snow and ice alert - as drivers face being stranded in chaos.
A cold plunge of air has pushed down from the Arctic and is now moving across the UK.
Much of the country will be dusted with frost or blanketed with snow and ice - sparking misery on the roads and railways.
Met Office expert Andy Page said: "There will be widespread frost this week and we could see some fairly deep laying snow in parts of northern UK.
"Strong winds could result in drifting or blizzard conditions at times.
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"The snow and ice will be disruptive and could potentially impact travel plans, make driving dangerous and pavements slippery.
"It will feel bitterly cold with daytime temperatures in the low single figures for many.
"Overnight temperatures will fall to -3 or -4 in many towns and cities, and it will be even colder in many rural areas."
Andy added that weather warnings could change quickly - so Brits should keep an eye on the latest Met Office updates.
The UK Health and Security Agency has now issued a cold health alert for England.
UKHSA extreme-weather boss Agostinho Sousa said: "The temperatures we will see can rapidly have a serious impact on the health of those over the age of 65 and those with pre-existing health conditions.
"It increases the risk of heart attacks, strokes and chest infections.
"It is therefore vital to check in on friends, family and neighbours to ensure they are well prepared for the cold weather this week."
Bleak conditions mean that drivers could face being stranded amid widespread travel chaos.
The RAC said it expected Monday to be its busiest day of the winter so far for vehicle breakdowns.
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While the Met Office had already issued yellow weather warnings covering today and for four days straight it has now extended the areas affected on Wednesday and Thursday.
Previously, for both those days the area affected stretched across northern Scotland to Northern Ireland and then down the west coast as far as south-west Wales.
Now, a mixture of sleet, snow and ice could also cause travel disruption in northern England from midnight on Wednesday until noon the same day, the Met Office has warned.
While southern Scotland is now entirely covered in an ice warning.
On the positive side, south-west Wales is no longer expected to be hit.
The same original warning had been in place for Thursday but now this has been extended across more parts of central Scotland as well as more parts of north-west England and parts of West Wales.
The forecaster said on X, formerly Twitter, there could be as much as two inches of snow falling in some parts today.
The Met Office said snow showers are likely to affect coastal areas with some places seeing 2-5cm of snow.
Motorists face a tough time and could end up being stranded as Arctic air sweeps in.
A severe weather alert has been issued by National Highways for snow affecting the north-west, with road users advised to plan ahead, and some rural communities warned they could be temporarily cut off.
Rail commuters on the Chiltern main line also face travel chaos following a landslip near Bicester, Oxfordshire.
The line between London Marylebone and both Birmingham Moor Street and Oxford as been closed as Network Rail carry out repairs.
Chiltern Railways issued a "do not travel" alert as the line is not expected to reopen until 7am on Tuesday, causing major disruption to journeys.
Met Office meteorologist Liam Eslick said that temperatures will be about 5C to 6C lower than usual for this time of year.
Mr Eslick said: "Especially towards the North where we do have these warnings, we're likely to see some travel disruption.
"So we would recommend people stick to the main roads and avoid country lanes where possible.
"These are the places that aren't going to see any gritting or any road clearances for the next couple of days.
"So we recommend people take their time, make sure they have time to do their cars in the mornings, and go steady."
He said: "So essentially we're looking at a strong northerly wind which is bringing in Arctic airmass which is cold, which is bringing in these wintry showers."
He said that "icy conditions" were expected, with maximum temperatures of 0C in parts of Scotland, and only 2C to 4C in southern parts of the UK.
The rest of the working weeks doesn’t look to be any better either with the Met Office issuing four days of ice alerts in total.
Snow is predicted for windward coastal areas, mainly in Northern Ireland and Scotland along with eastern East Anglia and north-west Wales and north-west England.
These areas are covered with a yellow weather warning from the Met Office, indicating there could be travel disruption in those areas.
People living in those areas can expect: “Some roads and railways affected with longer journey times by road, bus and train services.
“There is a small chance that power cuts will occur and other services, such as mobile phone coverage, may be affected.
“There is a slight chance that some rural communities could become cut off.
“There is a slight chance of snow-covered roads leading to stranded vehicles and passengers, along with delayed or cancelled rail and air travel.”
While there could be plenty of winter sunshine it will feel cold.
Brisk winds in the north and along eastern coastal area will bring a significant wind chill.
After sunset, temperatures will plummet leading to a widespread and in some parts severe frost.
While it will remain dry with clear skies for most, snow showers will continue in the north.
Another yellow weather warning is in place for Tuesday which covers all of Northern Ireland and all of Scotland as well as north-west England and parts of north Wales.
Once again travel disruption is likely.
It will remain cold and frosty for all with windward coastal areas also seeing showers.
An area of more significant rain, sleet and snow affecting northern areas is expected during the day.
While other areas are forecast to be dry and sunny.
The yellow weather warnings for Wednesday and Thursday cover northern Scotland and Northern Ireland and then stretches down the western coast, as far as south as south-west Wales.
Those wintry showers will persist and while there will be sunshine, it will remain cold with frost and ice appearing overnight.
Snow showers continuing for windward coasts throughout the week.
Temperatures are likely to pick up late on Friday as rain arrives.
Met Office Chief Meteorologist, Andy Page, said: “Where and how much snow we will get will vary throughout the week and weather warnings could change quickly, you will need to keep an eye on the forecast for your region for the latest information.
“There will be widespread frost this week and we could see some fairly deep laying snow in parts of northern UK and strong winds could result in drifting or blizzard conditions at times.
"The snow and ice will be disruptive and could potentially impact travel plans, make driving dangerous and pavements slippery.
“It will feel bitterly cold with daytime temperatures in the low single figures for many, and overnight temperatures will fall to -3 or -4 in many towns and cities, and it will be even colder in many rural areas.”
