Coldest November night on record in parts of UK
Temperatures plummeted to the coldest on record for November in parts of the UK overnight.
Northern Ireland hit a new low of -9.5C (15F) at Lough Fea, Co Tyrone, and in Wales, a record minimum of -18C (0F) was reached at Llysdinam, in Powys.
Snow is still falling in Scotland, Northern Ireland and north-east England, and Edinburgh, Glasgow and Derry airports have been closed.
Forecasters say the cold spell will continue well into next week.
Met Office severe weather warnings for heavy snow and widespread ice remain in place for eastern and central Scotland, and eastern England from the Borders down to the East Midlands.
Snow is also falling in Northern Ireland and north Norfolk, with some flurries possible in the southern-most counties of England.
BBC weather forecaster Alex Deakin said 10cm (4in) fell in Aberdeenshire in just two hours on Sunday morning, with a further 15-20cm (6-8in) likely in Fife, Perth and Kinross and Angus during the rest of the day.
That follows up to 40cm (16in) in parts of north-east England and Scotland on Saturday - said to be the most widespread snow at this time of year since 1993.
The coldest place in Scotland overnight on Saturday was Loch Glascarnoch, in the Highlands, at -15.3C (4F).
In England, the coldest spot was Topcliffe, North Yorkshire, where the mercury fell to -13.5 °C (8F).
Drivers are being urged to take care in the worst-hit areas and to travel only if necessary. The M9 in Stirling and the A1(M) in County Durham are particularly hazardous.
A 40-year-old man was seriously injured in a crash on the M1 near Sheffield on Saturday morning. His car skidded off the carriageway after hitting a patch of ice, and he was struck by another vehicle when he stepped out onto the hard shoulder.
Motoring organisation the AA said it had received 10,500 call-outs by 1430 GMT - compared with about 7,500 for the whole of an average November Sunday.
"We're getting about 2,000 calls an hour - that's virtually unheard of for a Sunday," spokesman Gavin Hill-Smith said.
Edinburgh, Glasgow and City of Derry airports are closed due to heavy snow, and there are also delays at Aberdeen, Newcastle, Durham-Tees Valley and Jersey airports.
Ian Mercer, who runs a company which supplies salt for gritting to schools, hospitals and shopping centres, told the BBC: "People are being much more proactive. Last year was the busiest ever, but we've already sold twice as much this year and it's not even December.
"We've had to import salt from places like Russia, Egypt and Sardinia but even there it's becoming more and more difficult to source.
"If it continues to be this cold beyond Christmas I think there will be really serious shortages."
Several weekend race meetings were called off due to the snow, as is Monday's event at Ffos Las, in Carmarthenshire.
Scotland's Alba Cup final, Dundee United's Premier League game against Rangers, and several FA Cup second round fixtures were also postponed.
Newcastle United's game against Chelsea will go ahead after extra staff were drafted in to clear the pitch.
A man died after jumping into the icy River Lune in Halton in Lancashire on Saturday in an attempt to save his pet springer spaniel.
The easterly winds show no sign of letting up, with the cold weather expected to last until next week at least.
Mr Deakin said: "As we go into Monday, one feature which will become significant is the wind. From Siberia, it will pick up quite significantly from Monday through to Tuesday. It will feel quite bitterly cold.
"Temperatures on the thermometers will be around 1C but it will feel much colder than that."
- Lakes, Rivers & Sea
Temperature tab only
The unusual weather is being caused by high pressure over Greenland and low pressure in the Baltics, forcing cold winds from the north-east across Europe.
The lowest ever recorded temperature in the UK was -27.2C (-17F) in Altnaharra, in the Highlands, in 1995.
England's lowest was -26.1C (-15F) in Newport, Shropshire, in 1982. The lowest in Wales was -23.3C (-10F), recorded in Rhayader, Powys, in 1940, and in Northern Ireland was -17.5C (1F) in Magherally, Co Down, in 1979.