Heavy snow has blanketed Britain as the first widespread big freeze of the winter brought dumps of up to 16cm, grounded planes and raised fears of transport chaos.
Around a third of Sunday's flights have already been cancelled from the west London airport amid forecasts of up to 15cm of snow, reduced visibility and the possibility of freezing fog.
With most of the UK on amber alert, the Met Office's second highest severe weather warning, flights were cancelled and a string of sporting fixtures fell victim to the big chill.
It came after Britain shivered through the coldest night of the winter so far on Fridaywith temperatures plunging to minus 12.4C.
Flurries fell over Scotland, northern England and the Midlands this afternoon before moving down to London and East Anglia.
Church Fenton in North Yorkshire recorded 16cm of snow, while up to 15cm was forecast for parts of Cumbria, Lincolnshire, East Anglia, North Yorkshire, the Peak District and the Midlands.
Most parts of the country are expected to wake up to between 5cm and 10cm Sunday morning.
A thick covering is also expected to fall on Heathrow Airport where a third of Sunday's flights have been axed amid adverse weather conditions and the possibility of freezing fog.
Passengers travelling through Gatwick were warned to expect some disruption and delays, with cancellations remaining a possibility.
Stansted, Luton and Birmingham Airports have all been closed due to snow.
On the roads, motorists faced what the RAC described as a "dangerous cocktail of driving conditions" and were urged to stay at home where possible. Some minor routes closed altogether.
The Highways Agency extended its amber alert until 9am Sunday, meaning there was a "high probability" of severe snow and a risk of difficult driving conditions.
Kevin Andrews, RAC patrol ambassador, said the wintry weather and sub-zero temperatures had left roads "extremely treacherous".
"It looks like we're going to get a dangerous cocktail of driving conditions this weekend," he added.
The motoring organisation said it had attended 70 per cent more breakdowns than normal while a spokesman for the AA said it dealt with around 1,500 call-outs per hour
The total figure was predicted to reach up to 15,000 by the end of the day - almost double the 8,500 of a usual Saturday.
Leicestershire-based developer Ben Marsh has also set up an online interactive map, encouraging Twitter users to tweet news and pictures of snow in their area using the hashtag #uksnow.
The Met Office 's amber alert in England applies to Yorkshire and Humber, the West Midlands, East Midlands, the East, the South West, London, the South East and the North West.
A yellow alert, which warns people to "be aware", was in place for parts of Scotland, Wales and south-west England.
Much of England is also under a cold weather alert of level 3, which warns of "100 per cent probability" of severe cold weather, icy conditions and heavy snow.
The forecast shows the snow is likely to settle and much of Britain will remain carpeted in white into next week.
While the mercury dropped to minus 12.4C in South Newington, Oxfordshire, Friday night - the lowest recorded temperature this season - it is expected to remain considerably milder Saturday night with lows of minus 4C before falling again next week.
The icy spell has already seen daytime temperatures plummet four or five degrees lower than average for February - traditionally the coldest month of the year.
The Department for Transport has said it was better prepared than ever for severe winter weather.
Salt stocks across Britain stand at more than 2.4 million tonnes - a million more than last year.
But they were of little comfort to sports fans hoping to see Portsmouth's home match against Hull City which became the first Championship fixture cancelled due to a frozen pitch.
The Doncaster versus Reading match was similarly postponed while a number of other lower league contests were called off.
Racing was also heavily hit but the ice did not deter swimmers who plunged into the Serpentine in London's Hyde Park this morning, despite its partially frozen waters.