It's provisionally been the coldest day in the UK since December 2010 - the temperature recorded in Braemar, Aberdeenshire dropped to minus 9.3 Celsius (15F)
A spokesman says northern Scotland could also record even colder temperatures tonight after breaking the record for the coldest night of the year earlier
The Met Office issues a yellow snow and ice warning covering northern Scotland and north-east England from midnight tonight until noon on Thursday
Forecasters also say there's a risk of ice across much of the South East, including London and Brighton until 11am on Tuesday
Meanwhile, three boys aged eight, 10 and 11 have died after falling in an icy lake near Solihull on Sunday
Officers entered the water and one tried to punch through the ice to save them, West Midlands Police said at a news conference
We're seeing travel disruption in many parts of the country and will be bringing you updates here.
In London, many Tube lines are facing delays, with the London Overground also affected.
The Met Office issues warnings of ice, fog and snow as weather wreaks havoc on transport.
BBC Weather presenter Carol Kirkwood gives the latest weather forecast as snow hits most of the UK.
Simon King
BBC weather presenter and meteorologist
The lowest temperature last night got down to -15.6C in Braemar, Scotland, which makes it the coldest night of the year and coldest since February 2021.
With Met Office warnings for freezing fog, ice and snow across many parts of the UK, there will clearly be more disruption from wintry weather through the day.
Parts of Bristol, Gloucester and Cirencester have been covered in snow as showers spread from west to east.
Enough snow fell for people to get their sledges out and enjoy the cold weather, after the region saw its first snow fall of this winter.
Southeastern Railway is warning rail passengers against travelling this morning due to the weather disruption.
In a statement, the rail company said snow and ice caused "severe disruption" across the whole Southeastern network on Sunday evening, and services would continue to be disrupted this morning.
Lines currently suspended include:
Trains will start later on the following routes, and services are expected to be severely disrupted this morning:
The runway at London Stansted Airport has reopened and been operational since 03:00 this morning, the airport has told the BBC.
All flights from the airport had been suspended earlier on Sunday night to clear snow.
There have also been delays at Heathrow and Gatwick.
After snow hit many parts of south-east England yesterday, some people ended up sleeping on a pub floor overnight after being snowed in in Sussex.
Dr Alexandra Loske, an art historian and curator, said she was forced to walk two miles to another pub in the snow to seek shelter on Sunday afternoon after she was "kicked out" of the first pub she was in - along with its other guests.
They ended up at The Bear Inn near the village of Burwash, which she said took in dozens of people and stayed open all night so people could shelter.
"It is all quite biblical," she wrote on Twitter on Sunday evening.
"Many of us sleeping on the floor tonight, but we are all happy."
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Image source, Getty ImagesYellow warnings, meaning conditions will make it difficult to travel, are in place until Monday morning for:
Motorists were urged to only travel on roads in the south-east of England on Sunday night if essential.
Kent was particularly hit hard, with snow severely affecting the M2 and parts of the M20, National Highways said.
The AA has told motorists to adjust their driving to the freezing conditions on Monday morning.
Image source, PA MediaThe cold weather warnings came as four children were taken to hospital in a critical condition after being rescued from an icy lake near Birmingham.
They are believed to have fallen into the water after playing on ice in Babbs Mill Park, Kingshurst. They were taken to two hospitals in Birmingham.
West Midlands Ambulance Service said the children had been in cardiac arrest when they were rescued, but offered no further update on their condition.
Read in full here.
A bout of cold weather across the UK is causing widespread travel disruption this morning.
All flights at Stansted Airport were suspended overnight, although they have now resumed, while there are delays to flights at Heathrow and Gatwick, after snow, ice and freezing fog swept across the UK.
Trains have also been delayed and drivers warned to take care after several motorway accidents.
A yellow weather warning is in place for Scotland, London and south-west England until Monday morning, with disruption expected to continue.
Read more here.
Hello and welcome to our live page coverage as the cold weather causes widespread travel disruption across the UK.
Stick with us for live updates.