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.
A spokesman said: "Councils have invested in new fleets of GPS-tracked gritting trucks, mini-gritters and specialist vehicles for narrow and hilly streets. Thousands of grit bins have been placed in estates and side streets, residents have been given their own bags of salt along with salt spreaders in some neighbourhoods and arrangements have been made with parish councils, farmers and community groups to grit hard-to-reach areas.
"Council websites will be updated with the latest information on weather, gritting routes, school closures and bin collections, special 'gritter Twitter' feeds and Facebook pages have been set up and leaflets have been sent out advising residents on winter services, how to drive safely in snow and dispelling the health and safety myths about clearing pavements."