The Met Office's warning stated that the cold wave from Norway, dubbed as the "Troll of Trondheim," could see snow showers and ice across huge parts of the country. Temperatures are also likely to fall to about -10 C.
Alex Deakin, a meteorologist for the Met Office, said that early modeling for the middle of this week shows that snow could affect Britain when a low pressure system drifts up and moist air hits the colder temperatures, bringing heavy snow across parts of the south.
He added that there could be "significant" snow in the middle parts of England and Wales. Deakin mentioned that if the low-pressure system moves toward France instead, it will bring cold north and northeasterly winds for an extended time in the U.K., but with snowfall limited to southern England.
London Mayor Sadiq Khan agreed to implement emergency planning which includes sheltering homeless people in the capital against the severe weather.
The Met Office has predicted that icy conditions with overnight double-digit sub zero temperatures in exposed parts of the U.K. could last for at least a week.
The Weather Outlook forecaster Brian Gaze said: "In the southern half of Britain, temperatures will probably plunge to between -5 C (23 F) and -10 C (14 F) in some locations and in the Welsh valleys they may fall below -10 C (14 F)."
"Forecast details become much more uncertain next week, but some computer models are showing areas of low pressure starting to push up from the southwest. It is only one possible scenario being shown by computer models at the present time, but if it happens the chance of disruptive snow in the southern half of Britain will increase."
London Mayor Sadiq Khan approved the implementation of an emergency plan that involves sheltering homeless people in the city against the harsh weather.
Meanwhile, public health chiefs had also asked people to give priority to heating their living rooms during the day to survive the cold. (Related: Brutal cold wave in Europe leads to record-high energy prices)
The U.K. Health and Security Agency stated that main rooms should be kept to at least 18 C (64.4 F) to avert dangerous situations amid fears that cost of living pressures will hinder households from turning on the central heating even with temperatures reaching -10 C (14 F).
Meanwhile, drivers have been asked to be careful on the roads after a night of freezing low temperatures.
The frosty blast has prodded the RAC to advise motorists about driving in icy conditions, along with checking tires, seeing they are properly inflated and have good tread.
RAC spokesman Rod Dennis added that oil, coolant and screen wash levels should also be topped up "if needed."
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