Heavy snow has intensified across Wales and central England as forecasters warned poor weather was moving north.
More snow was predicted to fall on Friday
Many commuters had a difficult journey home with 10cm of snow expected to fall across the Midlands.
But the snowfall could reach up to 20cm over the Pennines later as a Met Office severe weather warning remained in place on Friday evening.
With black ice and freezing fog forecast, motorists in affected areas were urged not to drive.
'Next in line'
Herefordshire, Worcestershire, Shropshire and south Wales were all the worst affected, with 25cm of snow recorded in Sennybridge, Powys.
But Sue Powell from the BBC Weather Centre said it will hit other parts of the country as Friday evening progresses.
She added: "The North Midlands, north Wales and the Pennines are all next in line.
"The snowfall has intensified across west and central parts today, but people further up the country should prepare for it to reach them."
She added that there was a risk of flooding in Wales, south-west England and the West Midlands with rain forecast for Saturday and a thaw likely.
Roads had been quiet early in the day as many workers commuters staggered their journeys. The Highways Agency said there were 400 gritters out in the morning.
But workers slipping off home early led to gridlock in some places, with the M5 solid for 15 miles from junction five at Bromsgrove.
A British Legion Club near Malvern, Worcestershire, is offering warmth and refreshment to stranded drivers, with many of the steep hills on the main route to Hereford impassable.
Around 250 cars were abandoned on the A4103 from Hereford to Worcester as drivers sought refuge.
Motorists were urged by police to stay in their vehicles if they broke down.
In a statement, West Midlands Police said conditions in Birmingham were "continuing to deteriorate", and advised drivers not to travel though the city centre unless it was absolutely necessary.
"There is now ice on some of the major roads in Birmingham and driving is nearly impossible," it continued.
Murray MacGregor from West Midlands Ambulance Service said the situation on the roads was so bad that crews were having difficulty responding to emergency calls.
He said: "We really need people to think whether they need to dial 999, especially if it's for something like a stubbed toe which we had earlier this evening.
"We are still working extremely hard. But the roads are now so gridlocked right across the area that it is affecting our ability to respond to 999 calls."
Birmingham Airport's runway was closed from 1630 GMT to 1945 GMT to due to heavy snow on the runway.
A spokeswoman said passengers should turn up at the airport for scheduled flights, but warned: "Once we can get people in the air again there will be some delays."
But across England and Wales most flights returned to normal, although travellers were warned to take extra time because of a possible backlog from disruption on Thursday.
Network Rail later said the situation was as "good as normal" for train companies.
The poor weather is expected to last into the weekend and early next week, although it is expected to be milder with snow giving way to sleet and rain.
However, Aberdeen and Angus in north-east Scotland could be set for further snowfall on Saturday.
Thousands of children were off school for a second day in Wales, Birmingham, Buckinghamshire, Worcestershire, Herefordshire and Oxfordshire.
Some parents, forced to take time off work to care for their children - or pay others to do so - feel that some schools have been over-reacting.
Disruption caused by the thick blanket of snow since Thursday is thought to have cost hundreds of millions of pounds.
Commons Leader Jack Straw admitted that Britain could cope better with this type of weather.