Motorists were stranded, journeys delayed and hundreds of schools shut as once again parts of the UK were hit by heavy snow.

But even as drivers and householders dug themselves out, the Environment Agency was warning householders and business owners in some areas to prepare for a new threat – flooding, as river levels began to rise, swollen by the melting snow.

Four flood warnings were in place in Devon, Dorset and Somerset. Another 23 of the less severe flood alerts were published for the south-west and 17 for the south-east.

The worst of the snowy weather on Wednesday morning brought areas of south-west England, Wales and the Midlands to a halt.

Many motorists were stuck overnight on the M5 in Somerset when up to 9cm (3.5in) of snow fell. Some managed to find a bed in service station hotels while others had to sleep in their vehicles or emergency shelters.

Businessman Dave Hughes was among those who spent the chilly early hours in his car at Taunton Deane services. "I was trying to get back to the Midlands when it came pelting down," he said. "I skidded once or twice and thought it was just best to pull in and get my head down. It's been a bit chilly but I've survived."

By mid-morning the snow was still causing trouble for motorists on the M5 with one lane shut in both directions near Cullompton services in Devon.

Dozens of A-roads in the west country were impassable including a stretch of the A39 near Bridgwater, which was blocked by snow and fallen trees.

Around 30 motorists had to be rescued and were given a place to sleep in a parish hall. Inspector Adam Crockford, of Avon and Somerset police, said: "It was a group effort by the emergency services and a bit of community spirit."

Once more, the snow gave hundreds of children an extra day off and provided a headache for working parents. More than 90 schools were closed in Somerset and Bath and north-east Somerset and about 40 were shut in the West Midlands.

South Wales was also badly hit. Snow and ice made driving conditions from Newport to Swansea difficult, while speed restrictions were in place around Cardiff and the old Severn Bridge. North of the M4 corridor, especially in the valleys, communities were once again cut off as fresh snow fell on the thick crust of ice that has made life there tricky for almost a week.

Cardiff and Vale University Health Board cancelled some outpatient operations. Paul Hollard, the deputy chief executive for the health board, said: "The cold weather puts a great strain on hospital services so please consider using your local GP or pharmacy if you feel unwell."

More than 400 schools in Wales were closed.

Northern Scotland and much of the north of England had around 2cm (0.8in) of snow but were expected to have drier and sunnier conditions as the day goes on.

More flurries of snow are expected in some areas but the falls of Tuesday night and Wednesday morning are expected to be the worst for the time being.

Paul Gundersen, the Met Office chief forecaster, said: "Tuesday night's heavy snow across parts of the south looks like being the last of the heavy snow for a while, with just light flurries around on Wednesday. The weather will stay very cold, but mostly dry through the rest of the week with severe frosts and patchy fog at night continuing to make it very icy."

There should be warmer weather at the weekend but rain and strong winds are predicted on Saturday night and into Sunday with a risk of gales. There could be a little more snow on Sunday in the east and more cold air might cause problems in some areas by the middle of next week.

Sporting fixtures at the weekend remain in doubt in some areas, but punters are hopeful Cheltenham Trials Day will go ahead. Wednesday racing is on at Lingfield and Kempton, which lost its meetings on Monday and Tuesday owing to ice and snow.