Britain has endured its coldest night of the winter so far with temperatures plummeting close to -18C in some areas, forecasters said.
The record-breaking cold snap comes as families setting off on half-term getaways have been warned of "deceptively dangerous" road conditions.
Experts said the mercury had fallen to -17.8C in Chesham, Bucks, during the early hours of the morning and was expected to plunge even lower as the icy weather continues to grip the UK.
Claire Allen, forecaster for MeteoGroup, the weather division of the Press Association, said: "Overnight we have had the coldest temperatures this winter so far.
"Most places in England and eastern areas of Wales dropped to below -4C, with -5.8C at Heathrow and -5.5C in Nottingham.
"Motorists are going to have to be extra cautious in areas where there is still snow remaining as it will be frozen making the roads very icy and slippery."
The Met Office said it had probably been the coldest night in England since December 2010 with temperatures widely below -10C across Lincolnshire, Cambridgeshire, Oxfordshire, Hertfordshire and Bedfordshire.
A "yellow" severe weather warning instructing people to "be aware" of ice on roads has been issued by the national weather service across the whole of England and parts of Wales. A level three cold weather alert is also in place.
Ms Allen said the bitter temperatures would continue today with London, south-eastern areas and the Midlands struggling to get above freezing. Most areas should be dry and sunny, but cloud, rain and freezing drizzle could hit western parts of Britain, she added.
Scotland and Northern Ireland escaped the adverse temperatures overnight thanks to a warm front, with readings of between 5C and 10C expected today.
Tonight is also forecast to be bitterly cold in England with temperatures in London and the Midlands falling to around -6C while milder temperatures are likely on Sunday.
The freezing temperatures have led to the cancellation of a number of this weekends sporting fixtures with Crystal Palace's Championship clash with Doncaster postponed due to a frozen pitch and a number of games in League One and League Two axed.
The race meetings at Newbury, Uttoxeter and Warwick have also fallen victim to conditions.
With thousands of families expected to embark on half-term getaways this weekend, the AA cautioned drivers to take extra care, especially if travelling to mainland Europe, where they face the risk of "frozen" diesel.
President Edmund King said: "There are still treacherous conditions on many local roads around the country. We found that even on local roads that had been gritted, the rain washed off the grit and turned to sheet ice."
Motorists were also advised to be prepared by carrying warm clothing and emergency provisions on their travels and allowing extra time for their journeys.
Darron Burness, the AA's head of special operations, added: "With half-term next week, some families will be heading off on long car journeys.
"Before departing, check the traffic and weather reports as the road conditions are quite unpredictable at the moment and it only takes one incident to cause long tail-backs.
"Anyone driving to Europe should be aware that it's so cold over there that diesel fuel can turn waxy, blocking the fuel filter and stopping cars running."
The British Red Cross also warned of the health dangers of the severe weather.
Joe Mulligan, head of first aid education, said: "Severe weather in winter can potentially be life-threatening especially to the elderly.
"If you have elderly relatives and neighbours, be sure to call in on them regularly and make sure they are warm enough and have enough provisions."
A young man died after his car collided with a lorry in icy conditions on the A470 in Powys, south Wales early yesterday.
Meanwhile, the cold snap caused a series of problems on main line rail services with commuters in south-east England plagued by delays.
First Capital Connect (FCC), Southern and Gatwick Express train companies all experienced problems with morning rush-hour delays also hitting the London Underground.
Heathrow Airport reported no disruption to flights, with none expected over the weekend either as skiers head off to the slopes for the holiday week.