The Met Office has raised fears for the elderly and ill by issuing a serious England-wide weather alert as the nation shivers in freezing conditions.
The forecaster issued its first country-wide Level 3 Cold Weather Alert of the winter - the second most serious.
The alerts are tied in to the government's Cold Weather Plan and are relayed to organisations such as Age UK, which help the elderly through winter.
With temperatures this week as low as minus 6.2C in Pershore, Worcestershire, minus 6.1C in South Farnborough, Hampshire, and minus 5.7C in Hurn, Dorset, the Level 3 Alert is expected to remain in force until the weekend when the country is braced for snow.
The Met Office said: "This weather could increase the health risks to vulnerable patients and disrupt the delivery of services."
The only higher alert is Level 4, which sees normally healthy people at risk from the cold.
Across Europe, popular travel destinations are even worse off, with bleak temperatures such as minus 14C in Berlin, minus 17C in Prague, minus 8C in Paris, minus 13C in Stockholm and minus 20C in Warsaw.
In eastern Europe yesterday, 83 people had died from the cold after temperatures sank to minus 32C.
Michelle Mitchell, charity director at Age UK, explained how dangerous the conditions can be for the elderly.
"It may have been relatively mild so far this year but the winter can be a dangerous time for older people," she said.
"Many people believe that the only risk of winter weather is getting a cold, but the risk is much greater.
"Low temperatures raise blood pressure, which puts people at a greater risk of heart attacks and strokes, as well as increasing the likelihood and severity of flu and other respiratory problems.
"We want older people to be able to enjoy the winter and, most importantly of all, stay well.
"That is why we have linked up with the Met Office to get advance information to ensure that forewarned is forearmed when it comes to winter weather."
Britain's deep freeze has seen daytime temperatures plummet four or five degrees lower than average for February - traditionally the coldest month of the year.
Forecasters said Saturday will see a cold front sweep south and east across the UK from the west, resulting in snow where slightly milder air meets cold air.
The mercury - which hovered between 1C and 4C yesterday - is forecast to drop considerably today, with some areas remaining below freezing in the daytime and temperatures as low as minus 10C possible tonight.
Aisling Creevey, a forecaster with MeteoGroup, the weather division of the Press Association, said: "Today is set to be bitterly cold, with a few snow flurries in the east of England.
"There will be maximum temperatures of 3C and 4C but many places won't get above freezing.
"Overnight will be very cold, with temperatures down to minus 8C, maybe minus 9C and minus 10C in some places.
"As we go into Friday, we are looking at some snow showers affecting the eastern part of England, mainly in the south."
Ms Creevey said a 24-hour period from Saturday would see much of the country experience snow as a front moves in from the west.
She said: "Scotland could see between 5cm and 10cm of snow on Saturday, and there could be 2cm-5cm across England and Wales.
"But south west England is likely to see rain rather than snow."
Respite from the big freeze is not expected until Monday, when milder temperatures are expected, along with frost overnight.