Extreme cold will briefly give way to milder, more unsettled conditions due to sweep in from the Atlantic over the next 24 hours.

Torrential downpours threaten to lash swathes of the country with rain, sleet and snow through the week.

Arctic conditions will return on Thursday, opening the doors to further freezing temperatures and wintry downpours.

It follows days of winter chaos which saw heavy snow since the weekend spark chaos on the roads and transport networks.

Monday night was the coldest in more than a year after temperatures plunged to -13C (8.6F) in Shawbury, Shropshire.

The Met Office is predicting a brief let up in the cold on Wednesday before Polar winds sweep back across Britain.

Spokesman Grahame Madge said: “Wednesday will be slightly milder as we lose the Arctic influence and temperatures will rise into high single figures.

“Rain will start coming in however and some of these showers will fall as snow over high ground in Scotland and northern England.

“It looks as though we will return to a Polar maritime airflow towards the end of the week bringing temperatures back down with further wintry showers possible in parts on Thursday.

“Friday is looking calmer and more settled although it will be cold.”

Despite the rise in temperatures on Wednesday chilly winds and showers will make it feel cold and wintry, he added.

Melting snow and rain will cause lying snow to melt putting parts of the country at risk of localised flooding.

Temperatures are forecast to reach 8C (46.4F) in the south on Wednesday although northern Britain will hover between freezing and 4C (39.2F).

Lows of -6C (21.2F) are forecast across Scotland by the end of the week with much of the UK sinking to freezing or below.

WeatherOnline forecaster Simon Keeling said: “There will be a mix of rain, sleet and snow with temperatures varying through the week.

“It will turn briefly milder in the south mid-week before turning colder again later.

“There is a risk of some wintry weather passing south on Thursday ahead of a drier, cooler weekend.”

Netweather forecaster Jo Farrow said: “Into Wednesday there will be blustery winds and more rain moving eastwards with wintry bits mixed in.

“Hail, thunder and a low risk of flooding as the snow begins to melt and heavy bursts of rain move through.

“A much more unsettled look for midweek but not quite the bitter cold of Sunday.”

An Environment Agency spokesman said: “The Environment Agency will be carefully monitoring the potential for flooding impacts as the weekend’s snow melts through this week.

“As it melts, there may be a risk of river or surface water flooding impacts. 

“We will work with partners and communities as appropriate. We will issue flood alerts and warnings as needed.”