Temperatures are continuing to fall with the arrival of the first cold snap of the season.
There have already been wintry showers in Scotland and forecasters predicted more north of the border and down the east coast.
The mercury is not expected to rise much above zero on Friday night in many areas.
Tony Conlan, a forecaster with MeteoGroup UK, the weather division of the Press Association, said some areas of lower ground in Scotland saw their first meaningful snow and a "wintry mix" of rain, sleet, hail and some snow will continue until late on Saturday.
"It will be colder than it has been, with temperatures typically ranging from 2C (36F) in parts of the Scottish Highlands to 10 or 11C (50-52F) in the far west of England," he said. "Late on Saturday night there should be milder air coming in from the north west making it warmer on Sunday but still not very pleasant, with rain just about everywhere."
The Local Government Association (LGA) said that hundreds of gritters are on stand-by to treat roads as required.
An LGA survey of councils across England and Wales found there is currently about 1.3 million tonnes of salt in council depots - enough to fill more than 400 Olympic-sized swimming pools. This is about twice as much as was used during last winter.
Thousands of migrating birds have been dying before reaching England this week because of an appalling combination of fog and winds around the coast, according to the Royal Society for the Protection of Birds (RSPB).
Some fishermen have told the charity of the deaths of many exhausted and disorientated "garden" birds plunging into the sea around their vessels, a spokesman said.
England's east coast, from Northumberland to Kent, has seen the arrival of many birds, including redwings, fieldfares, bramblings and blackbirds, perhaps numbering in their millions.