The Met Office has raised its severe cold weather alert to level 2, meaning there will be a danger to life as an icy blast brings the chilliest nights of the season.
Frigid temperatures pose serious health risks to vulnerable Britons and threaten to disrupt the delivery of NHS services between Thursday evening and Monday morning, according to forecasters.
Overnight temperatures are expected to plunge below zero in some parts of the UK, freezing fog could disrupt travel and frost is likely to be widespread. Daytime temperatures will be chilly, especially in the north.
The Met Office said the “greatest period” of cold weather is likely in the 48 hours from 6pm on Thursday, and the chilly conditions are expected to last into next week as the calendar turns to December.
Level 2, which is assigned the colour yellow on the four-level scale, means a state of “alert and readiness” for forecasters and NHS trusts.
The alert level covers the North West and North East regions of England, where daytime temperatures may struggle to climb above 5-6C on Friday.
The Met Office said: “There is a 60% probability of severe cold weather between 6pm on Thursday 26 November and 6am on Monday 30 November in parts of England.
“This weather could increase the health risks to vulnerable patients and disrupt the delivery of (NHS) services.
“High pressure over the UK will lead to an increased likelihood of lower temperatures from Thursday evening, perhaps lasting until Monday, with the greatest period of cold weather likely in the first 48 hours.
“The centre for the cold weather is expected to be across northern England, in particular higher ground.
“Locally persistent fog may also play a role in reducing daytime maximum temperatures, especially in North East England on Thursday and Friday, but there remains some uncertainly on this and therefore the risk reduces slightly through Sunday.”
The alert system is used to encourage social and healthcare services to take action to protect vulnerable Britons from cold weather.
The Met Office said: “Prolonged periods of cold weather can be dangerous, especially for older people, those with underlying health conditions, and young children.”
Those who are at risk should stock up on food and medicine so they don’t have to go out into the cold, and keep their homes heated to at least 18C.
Met Office five-day weather forecast
Most parts dry with light winds and sunny spells, though a few stubborn fog patches may persist.
Cloudy in the far south, perhaps with a little rain at times.
Rather chilly for many.
Some rain for north-west Scotland.
Perhaps cloudy with a little rain in the far south of England.
Turning frosty elsewhere with freezing fog patches, perhaps dense in places by dawn.
Fog patches will be slow to clear, perhaps persisting in places, and feeling cold.
Some rain for north-west Scotland, whilst also perhaps across southern England and Wales later.
Saturday to Monday
Rain in west and north-western areas, otherwise fog patches thinning to sunny spells Saturday.
Rainy and windy in the far north Sunday and Monday, frost, fog clearing to sun elsewhere.