Families setting off on half-term getaways have been warned of "deceptively dangerous" road conditions and sub-zero temperatures as the snow freezes.
Forecasters predicted another hard frost setting in, with the mercury set to plummet to minus 9C in some areas, but the bitterly cold weather is expected to ease over the weekend, with milder temperatures likely as the school holidays get under way.
The AA cautioned drivers to take extra care, especially if travelling to mainland Europe, where they face the risk of "frozen" diesel.
President Edmund King said: "There are still treacherous conditions on many local roads around the country. We found that even on local roads that had been gritted, the rain washed off the grit and turned to sheet ice. With further snow falls last night we now have some deceptively dangerous roads with a light cover of snow and sheet ice below.
"Drivers need to expect the unexpected and drive with extreme caution on local roads. It doesn't matter what vehicle you are in but if you get a heavy downpour of rain that almost instantly turns to ice, it is very difficult for grit to be effective."
Motorists were also advised to be prepared by carrying warm clothing and emergency provisions on their travels and allowing extra time for their journeys.
Darron Burness, the AA's head of special operations, said: "With half-term next week, some families will be heading off on long car journeys. Before departing, check the traffic and weather reports as the road conditions are quite unpredictable at the moment and it only takes one incident to cause long tail-backs.
"Anyone driving to Europe should be aware that it's so cold over there that diesel fuel can turn waxy, blocking the fuel filter and stopping cars running."
MeteoGroup, the weather division of the Press Association, said although Saturday would be a dry and sunny day in most areas, the weather in some western parts of England, north west Wales, Scotland and Northern Ireland would be largely cloudy, with rain or freezing drizzle. Temperatures of 1C or 2C were forecast around much of England and Wales, rising to 8C or 9C in Scotland and Northern Ireland.
Sunday is expected to be milder still.
But forecaster Sally Webb said: "There's likely to be a lot of ice, especially in northern areas where it's been raining today. People should be very careful on the roads as there are signs of ice forming and there's still snow lying around by the sides of roads, which is likely to freeze and become a hazard."