A severe weather warning for very heavy snowfall has been issued for parts of Berkshire.
Up to 8in (20cm) has fallen in the county and the Met Office said Slough, Bracknell, Windsor, Maidenhead and Wokingham could expect more heavy snow.
With temperatures around freezing or below, drivers have been warned to take extra care on the roads which are icy.
Police said motorists should plan their journey before setting out, but should only travel if "absolutely necessary".
They said the last weekend before Christmas was expected to be one of the busiest of the year on the roads.
A spokesman said: "Drivers are urged not to abandon their vehicles, especially where they may obstruct emergency service vehicles and major roads or motorways.
"If they do, the vehicles may have to be removed and it will be the driver's responsibility to pay for the cost of recovering them."
Drivers who do venture out on the roads are urged to prepare themselves by packing warm clothes and blankets, boots, food, drinks, a mobile phone, torch, jump leads, tow rope, first aid kit, warning triangle, de-icer and a shovel.
"Tell someone where you are going and when you expect to arrive," the spokesman said.