Snow and ice causes disruption as cold spell continues
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Large parts of the UK have been brought to a standstill by the early freeze
Thousands of schools shut by snow
Why do schools shut when it snows?
The UK is in the grip of one of the coldest starts to December in more than 20 years with snow and ice causing road, rail and airport chaos.
Temperatures plummeted to -16C (3F) in the Highlands and 4,000 schools across the UK were unable to open.
Edinburgh and Gatwick airports will be shut until at least Thursday, and there were rail cancellations and delays.
The Met Office has issued heavy snow warnings for much of the eastern side of Britain and some central areas.
Rail companies said they were working "flat out" to get as many trains running as possible.
The Forth Road Bridge was closed for the first time since it opened in 1964 but has now reopened.
In England, heavy snow warnings are in place for the North East, Yorkshire and Humber, East Midlands, East, and London and the South.
In Scotland the warnings apply to Grampian, Strathclyde, Central, Tayside and Fife, and South West, Lothian and Borders.
More than 250,000 Scottish children have had a day off - about 40% of all those of school age - many for the third consecutive day, with a third of councils closing all their schools.
Some local authorities have told parents that schools will remain closed for the rest of the week. In total, more than 1,500 of 2,722 schools were shut.
Continue reading the main story WEATHER AND TRAVEL INFO
Get the latest on school closures and travel problems via your local website
Check if snow is forecast in your area at BBC Weather
Details of motorway and local road closures and public transport disruption are available at BBC Travel News
For advice on handling difficult driving conditions, see the Highways Agency website
For information about severe weather warnings, see the Met Office website
For information about staying healthy in the cold weather, see the NHS Winter Health website
An avalanche warning has been issued in the Cairngorms, near Aviemore, where hundreds of skiers took to the slopes on Tuesday.
Police are advising people not to travel unless absolutely necessary - especially in the worst-hit areas of Scotland, Yorkshire, Derbyshire and south-east England.
Supt Chris Moon, of Surrey Police, said the county's conditions were the worst he had ever seen and were likely to deteriorate further.
He added: "I have put out several severe weather warnings in my career, but this one I really must stress."
Police in Kent have advised freight traffic not to enter the county unless absolutely necessary as gale force winds are forecast. Some roads in the west and north of the county are impassable due to snow and ice.
Thousands of rail commuters face severe disruption to their journeys in Scotland and northern England - particularly in the Sheffield area.
London and the South East has also suffered, including delays and cancellations to Southeastern services operating out of London Victoria and Charing Cross.
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All through the night we were promised buses from Hastings and other areas, none of which came”
Stranded rail passenger
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There are delays on the East Coast Main Line, with an hourly service between London and Edinburgh, and reduced services between London and both Leeds and Newcastle.
Passengers face delays of up to an hour on Eurostar services.
National Rail Enquiries has set up a telephone hotline for information about snow-related disruption on 08453 017 641, and also has updates at @nationalrailenq on Twitter.
About one third of all rail services were suffering delays or cancellations at Wednesday lunchtime.
Ashwin Kumar, of rail watchdog Passenger Focus, called on train companies to do all they could to make life easier for their customers.
He said: "We need better information systems so that we can cope when disruption does happen."
The Association of Train Operating Companies said rail operators and Network Rail were "doing all they can to keep trains moving and get people to where they need to be".
One of the worst affected areas of England is South Yorkshire, where snowfall of up to 30cm (12in) has brought parts of the county to a standstill.
About 300 schools are shut, bus services have been suspended in Sheffield, Rotherham, and Doncaster, and there are delays and cancellations on train services between Sheffield and Leeds, as well as flights being halted at Robin Hood Airport in Doncaster.
Hospitals in South Yorkshire are asking patients not to attend unless it is urgent, and they have asked off-duty medical staff to make their way into work if possible.
Sheffield City Council has cancelled a full council meeting for the first time and the Halifax Courier newspaper has not made it out, also for the first time, because it is stuck at the printers in Sheffield.
Overnight temperatures hit a low of -20C (-4F) in Altnaharra in the Highlands.
The early cold spell has taken everyone by surprise BBC weather forecaster Tomasz Schafernaker said there was 1m (3ft) of snow across parts of north-east England.
More heavy snow was expected on Wednesday afternoon and evening across southern England from Hampshire to southern Essex and possibly into London.
There could be up to 30cm of snow in southern England by the end of Thursday. There will also be more snow showers in north-east England.
On Thursday night, temperatures of up to -25C (-13F) to -30C (-22F) in some parts of Scotland are forecast.
The disruption on Wednesday includes:
Severe disruption for air passengers at Gatwick Airport where its runways are closed until 1000 GMT on Thursday. Edinburgh Airport is also closed until at least Thursday morning. Guernsey Airport, Robin Hood Airport in Doncaster and Durham Tees Valley Airport are also shut, while other airports are disrupted. Passengers are advised to check with their airline
Hundreds of school closures in England, including nearly 1,000 full or partial closures in West, North and South Yorkshire, about 330 schools in Essex, about 550 in the South East and Surrey, more than 800 in the East Midlands and 195 across Tyneside, Wearside, County Durham and Northumberland. In Jersey, all the island's schools were closed
The M8 motorway between Glasgow and Edinburgh is down to one lane in each direction
In Kent the M20 is closed with long delays for London-bound traffic between J3, M26 and J1, M25, because of ice, snow and a jack-knifed lorry.
In Derbyshire, one lane is closed on the M1 southbound, with delays between J29, A617 (Chesterfield) and J28, A38 (Alfreton), because of recovery work and a jack-knifed lorry
In West Yorkshire, one lane is blocked on the M62 in both directions between J23, A640 (Huddersfield) and J26, M606 (Chain Bar), because of snow
On Tuesday evening many drivers and rail passengers were stuck for hours as the weather worsened.
Tony Scott started his journey home from London to Tunbridge in Kent, at 1730 GMT on Tuesday and had still not arrived home 10 hours later.
He told the BBC he tried to pick up at train at London Bridge station but they were so overcrowded it was impossible to get on.
"My friend and I decided to grab a meal. When we returned to the station there was still no information on when trains may come. We asked station staff if the trains were cancelled and if it would be wisest just to find a hotel for the night. The staff... kept telling us the trains were delayed, which implied trains were coming.
"A train finally arrived at 0130, but it stopped at Orpington, stuck. All through the night we were promised buses from Hastings and other areas, none of which came. None of the staff on the train knew anything. My friend and I even phoned Southeastern, but no-one there even knew that our train was stuck."
He said the train started to travel back towards London at 1030 GMT on Wednesday, with passengers being told they would be returned to London Bridge before heading back towards Kent.
The AA had attended 11,300 breakdowns across the UK by 1500 GMT on Wednesday, with the busiest areas said to be London, especially the south of the capital, Yorkshire, Kent, north-east England and Aberdeen.
The motoring organisation said there had been a failure to deal with jams on motorways and major roads, and breakdown service Green Flag said local authorities had not spread enough grit on minor roads.
Halfords said an additional 16,600 sledges were being shipped in to meet increased demands.