A new severe weather warning of ice has been issued as wintry weather continues around much of the UK.
All of Wales and most of England is covered by the yellow Met Office warning, which is in place from Monday evening until Tuesday at 9:00 GMT.
Hundreds of schools closed in south-west England and Wales because of heavy snow.
Temperatures are expected to rise this week but the weather could turn colder again by the weekend, forecasters said.
Over 20cm (8ins) of snow has been recorded in central and southern England as temperatures fell widely below 0C overnight with lows of -5C in Scotland.
In Wales, a total of 207 schools were closed on Monday, with GCSE pupils at Brynmawr School in Blaenau Gwent being taught in a cinema instead.
Devon County Council said nearly all of their 307 schools were shut and the others partially closed, while 97 schools in Cornwall and 163 schools in Somerset were also shut.
Meanwhile, around 80 motorists sought refuge overnight at an emergency rest centre in a college near the A30 in Devon.
Among those stranded at the centre were a bride and groom on their wedding night.
Other stranded drivers camped in their vehicles at a service station on the A30 in Okehampton, which was blocked by heavy snow until it fully reopened in the morning.
Richard White, volunteer rest centre manager at Okehampton College - where 82 people, including children, spent the night - said: "It's the last thing you expect to get stuck in the snow.
"One lady said she felt like a refugee.
"It was -3C and it didn't stop snowing until 06:00. It's been a really horrid night."
Newly-married couple John and Sara Lund, who were travelling to their honeymoon in Cornwall, were forced to spend their wedding night at the rest centre.
The groom, Mr Lund, told BBC Radio 4's Today programme that he and his new bride spent their first night sleeping on a mat on "rock-hard floors" in a classroom with around 20 other stranded people.
"It's probably a story which has helped keep morale high in the camp," Mr Lund said.
A 64-mile stretch of the A30 from the M5 at Exeter to near Bodmin in Cornwall was closed by Devon and Cornwall Police to allow its officers and Highways England to clear the route.
The force warned drivers to only travel if necessary and "slow down".
The runway at Exeter Airport was closed but reopened just after 11:00 GMT, although some flights were delayed or cancelled.
Temperatures dropped across many parts of the UK overnight causing partly melted snow to refreeze.
In parts of England, temperatures fell to -2C and -3C and -5C in central Scotland.
Temperatures are expected to rise into double figures this week but could become colder by the weekend bringing some frost, BBC Weather said.
Met Office forecaster Craig Snell added: "Generally we are out of the woods but anyone hoping for a spring heatwave will have to wait."
Mr Snell said the UK should now see the start of a "gradual thaw" - but added there is still a risk of frost and ice, including on Tuesday morning.
He said the weather will become "briefly milder then turning colder come the weekend, but not as cold and not as snowy as the weekend just gone".