Britain is bracing itself for an icy blast this week when temperatures will plummet below freezing to bring snow and widespread frosts.

Forecasters predict that sleet and snow showers are mostly likely to hit on Thursday and Friday, with a chance the weekend will be affected as well.

Chris Bell from Norwich-based Weatherquest said he expected freezing overnight conditions too. “It will be chillier than it has been for most of the winter and late autumn,” he said.

“There is potential for sleet or snow showers at the end of the week. We will have high temperatures in the week of 5-7C (41F-44.6F) across the region which is about average for this time of year. We will then have lower temperatures overnight, about freezing or just above.”

This winter has been exceptionally mild so far, with temperatures way above average for this time of year. Temperatures on Christmas Day for parts of the region came to a comparatively warm 11-13C (51.8-55F). The chill weather - the first wintry spell for many - will be a sharp change from the mild weather last month, the wettest on record and the warmest ever December, when temperatures averaged 7.9C (46.2F).

Forecasters are predicting a wet start to the week, with wintry showers especially on high ground, before an area of high pressure towards the weekend will see temperatures struggling to reach 5C (41F) in the South and not rising above freezing further north.

Motorists, pedestrians and cyclists are being warned of the risk of frost and ice on roads.

During the early part of the week cold air will spread southwards, bringing the chance of frost, ice and, for some, the possibility of sleet, snow and hail, the Met Office said. Daytime temperatures are likely to be in the range of freezing to 5C (41F).

Southern Scotland and parts of north-east England, particularly the high ground over the Pennines, received a dusting of snow over the weekend and Billy Payne, a forecaster with MeteoGroup, said more was likely in the coming days.

Low pressure on Tuesday and Wednesday will move away to the East, and chill north-westerly winds will cause temperatures to drop off, with wintry showers on both days.