Temperatures are expected to plunge to minus 8C as weather warnings for snow and ice are set to remain in place over the weekend.
The UK Health Security Agency (UKHSA) has issued cold weather health alerts for all of England ahead of a week of low temperatures.
Amber alerts were issued from 12pm on Thursday until next Wednesday, meaning a rise in deaths is likely, particularly among those aged 65 and over or with health conditions.
Temperatures of between minus 4C and 5C were expected in parts of Wales and southern England on Thursday night, plunging to minus 8C in northern England and Scotland.
Dan Stroud, a meteorologist at the Met Office, said: “There’ll be widespread frost across the country from Land’s End to John O’Groats.
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“It will be comfortably below where we should be for this time of year and I would expect temperatures to hit minus 8C in parts of Scotland.”
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Mr Stroud confirmed conditions should become warmer by the end of this weekend before cold weather strikes again early next week.
He said: “The second half of the weekend should be in the high singles or low doubles.
“But temperatures will dive again next week, particularly on Monday and Tuesday.
“They should start to improve towards the latter end of the week. But there’s a lot of water to go under the bridge until then.”
The NHS Black Country integrated care board has warned the public to “avoid going out early when the frost is thick or late at night when it’s dark”, adding people should keep their hands free and wear shoes with a good grip.
In Herefordshire, the Wye Valley NHS Trust told people to “have sufficient food and medicine and take measures to reduce draughts in your home”.
London councils activated an emergency accommodation protocol on Thursday for people sleeping rough in freezing conditions.
The emergency measures, which see extra beds made available, have been active for three nights so far this winter.
Meanwhile, several weather warnings have been issued by the Met Office ahead of a blast of snow over the weekend.
The yellow warning indicates there could be icy surfaces in northern and western Scotland, the northwest of England and Northern Ireland.
It will remain in place until 10am on Friday morning, and could make for difficult travelling conditions, the forecaster warned.
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A snow and ice warning is also in place covering parts of northern Scotland until 10am on Friday.
A yellow warning for snow and ice is in place from noon on Saturday until late on Sunday night and covers all regions of England, other than the South West, Wales and parts of southern Scotland.
About 5cm of snow is expected widely across the Midlands, Wales and northern England, with as much as 20cm to 30cm over high ground in Wales and the Pennines, the Met Office said.
Strong winds could lead to snow drifts in some areas, and freezing rain as temperatures creep up could add to the risk of ice.
A separate warning for snow is in place for most of Scotland from midnight on Sunday until 12pm on Monday.
The cold snap comes as a major incident was declared in Greater Manchester by police on Wednesday after flooding forced homes to be evacuated and closed train lines and roads following heavy rain.
