Areas recorded lows of minus 17.7C (14F) today as the death toll continued to rise on another day of disruption.
Among casualties as heavy snow turned to ice was a 16-year-old boy killed after the car he was travelling in crashed and was in collision with a lorry on the A1 near Richmond, North Yorkshire.
Dwindling gritting stocks were also reaching crisis point as a series of accidents on some major routes added to difficulties for millions of drivers.
Meanwhile, there was growing anger on behalf of parents as hundreds of thousands of children were given another day off school. Manchester Council leader Sir Richard Leese attacked headteachers, saying many closures "seem to be unnecessary".
About 4,000 homes in southern England were also without power, with the worst affected area around Petersfield, in Hampshire.
Lows of minus 17.7C (0.14F) in Benson, Oxfordshire, and Woodford, Greater Manchester, eclipsed minimum temperatures at many of Europe's famous ski resorts.
The recordings also matched some recommendations for the ideal temperature for freezing food at home.
Andy Ratcliffe, forecaster from MeteoGroup UK, the weather division of the Press Association, said the Scottish Highlands will be worst hit by tonight's icy blast.
He said: "In England it will not be as extremely cold tonight as there will be a breeze. But in Scotland it could be the coldest night of the winter for Britain, with temperatures as low as the minus 20s in the Highlands.
"Snow showers will creep in to parts of East Anglia, Kent and Scotland again overnight and tomorrow.
"There will also be a windchill factor going into the weekend making many areas, even in daytime, feel like minus 7C."
Councils revealed they were being forced to spread grit more thinly on Britain's frozen roads as Prime Minister Gordon Brown spoke to the managing director of Salt Union, the Cheshire-based company which supplies two-thirds of the country's salt for gritting roads.
Harrow Council in north London described its wait for supplies as "pretty outrageous".
Cleveland Potash, one of the biggest suppliers of rock salt in the UK, said that as demand was outstripping capacity it asked the Department of Transport to draw up a list of customers to supply first.
Cheshire's Winsford salt mine also said it only has a few days' supply of surface salt left as a No 10 spokesman said there was no provision for central Government to take control of stocks.
The National Grid issued its second gas alert in three days as the UK's freezing weather pushed demand to record levels.
The operator's gas balancing alert came with gas demand expected to hit 454 million cubic metres today - higher than the all-time record of 449 million in January 2003.
Roads, trains and airports were subjected to another day of havoc.
British Airways axed flights at Gatwick and Heathrow and easyJet cancelled around 70 flights at Gatwick, while nearly all train companies reported disrupted services, with commuters suffering not only a reduction in frequency on some routes but problems caused by broken-down trains.
The Southern and Southeastern train companies were among those operating to revised timetables. There were no trains on Southeastern services between Sittingbourne and Sheerness-on-Sea, in Kent, and services were delayed between London Bridge and Cannon Street stations due to a broken-down train.
Among the latest round of mass school closures were more than 300 in Hertfordshire, several hundred in Hampshire and all but one in St Helens.
More than 500 schools were said to be shut in Wales, along with hundreds of others in Warrington, Cheshire and Gloucestershire.
The disruption is estimated to have cost businesses around £700 million alone, with much more financial damage to come as the country struggles to get back to normal.
Frontline services continued to be stretched. Sussex Police reported there had been more calls than officers received on New Year's Eve. North East Ambulance Service also underlined it was under "very challenging conditions"
* A crisis was averted in West Berkshire when 300 tonnes of grit were sourced from neighbouring West Sussex council, meaning that more than 400 miles of roads could be covered overnight. It had initially been feared that last night's gritting operation on A and B roads would be the last until the delivery.
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