Air, rail and road services were all severely disrupted as Prime Minister Gordon Brown said the authorities were doing "everything in our power" to ensure the resumption of key transport links.
An army of snow ploughs and gritters were working round-the-clock to clear roads as much of the UK was blanketed in snow.
Major airports closed runways and all British Airways flights from Heathrow Airport were cancelled until 5pm, as were all bus services in London and dozens of trains during the morning rush hour.
On the London Underground, 10 of the 11 lines were either completely or partly suspended as the "quantity of snowfall" disrupted services, a Transport for London spokesman said
One snapshot survey of more than 300 employers found one in five adults stayed away from work because of the extreme weather.
Speaking at a press conference with Chinese Premier Wen Jiabao at the Foreign Office in London, Mr Brown said: "We are doing everything in our power to ensure that the services - road, rail and airports - are open as quickly as possible and we are continuously monitoring this throughout the day."
London mayor Boris Johnson later suspended the city's congestion charge as a gesture of thanks to workers who were trying to keep the capital moving.
Motorists, who were warned only to make essential journeys, were caught in tailbacks of more than 50 miles and queues of up to two-and-a-half hours as they battled against the heavy snow across the country.
Helen Chivers, a forecaster with the Met Office, said the last time the UK saw such widespread snowfall was in February 1991.
"And we're going to get more," she said.
A large area of sleet and snow showers was moving out of France on its way to the UK.
"It's winter for a change," she said.
"The last two have been really mild, really wet and really windy.
"We don't get this very often."
There were 11cm of snow at Heathrow Airport, 25cm over the North Downs in Kent and Surrey, 8cm along the eastern side of the Pennines and 1cm across the Welsh border.
More than a thousand primary and secondary schools were forced to shut their doors due to the adverse weather conditions. Schools in southern England were among the worst affected.
At Heathrow Airport, a Cyprus Airways flight, CY 332, from Larnaca strayed onto a grassed area while taxiing to the terminal building after landing shortly after 8.30am. None of the passengers were injured.
Both of the airport's runways were temporarily closed before one later re-opened and passengers faced severe delays and disruption at airports across the country.
A number of train services linking London and the south coast were also delayed or cancelled as snow drifted on to the tracks.
Eurostar said it was operating services between the UK and the Continent but that they were subject to possible delays.
A London Ambulance Service spokesman said it would only respond to "life-threatening calls" as the heavy snow and dangerous driving conditions meant it was under "severe pressure". The service received more than 650 calls between midnight and 7am today.
A spokeswoman for navigation firm TomTom said there were more than 1,000 miles of jams around the country, with one of the longest being 53.8 miles on the M25 between between junction 19 at Watford and junction 8 at Reigate, at 8.45am. Drivers were delayed for more than two-and-a-half hours.
The snow also caused travel chaos across the country with numerous collisions and "treacherous" driving conditions, police said.
Multi-vehicle pile ups temporarily closed a stretch of the M5 near Tewkesbury, Gloucestershire, and the A1(M) between junctions 35 and 36, near Doncaster. There were no reports of serious injuries.
The Scottish Ambulance Service said two members of an ambulance crew suffered minor injuries and were taken to hospital after their vehicle overturned in snowy conditions on the A909 as they responded to a 999 call at Kelty, Fife.
A 17-year-old pedestrian was injured after being hit by a car near all-boys William Parker School in Hastings, East Sussex, and police in Cleveland said a bus overturned off the A173, at Newton of Roseberry, but no-one was injured.
Last night, three teenagers were rushed to hospital after their car collided with another on a patch of ice in Shropshire. A 15-year-old girl, along with two boys aged 17 and 18, were taken to the Princess Royal Hospital in Telford with minor injuries.
The snowy conditions also forced the closure of the Old Bailey in central London and several other crown courts, including Southwark and Blackfriars.
Meanwhile, Age Concern urged older people to take extra precautions to keep warm and safe at home.
Asked about the impact of the snow on the economy, Dr Helen Hill, director of policy and public affairs at the London Chamber of Commerce and Industry, said: "We know that a one-day closure of the Tube alone can cost the capital up to £48 million in lost productivity, so with most of London's transport infrastructure down, the costs could be similarly high."
Elsewhere, the cold snap brought the unusual sight of snow on the beach and along the harbour at Sandbanks in Poole, Dorset.
And the picturesque village of Middleton-in-Teesdale, in County Durham, was under six inches of snow, residents said.
Carol Mitchell, the village Post Mistress said although the snow had made life difficult for many people living there, the "Dunkirk spirit was kicking in".
"It has been bad today," she said.
"It is snowing hard and the forecast says there is more to come. But it is amazing how many people are out and helping."
Councils should not be used as scapegoats by organisations caught out by today's weather, the Local Government Association (LGA) warned.
Chairman of the LGA environment board Councillor Paul Bettison said: "Other organisations that are affected by the snow appear to be using councils as a scapegoat for their own poor preparations for the weather.
"The claim that it is local authorities' fault that they cannot run services needs to be treated with a huge pinch of gritting salt.
"With the worst conditions hitting the country in almost two decades, councils are battling round the clock to not only grit the roads and the pavements, but to keep vulnerable older people safe and inform parents that schools are closed.
"Swathes of the country are being hit by up to 6in of snow and hundreds of council workers are gritting pavements and roads. But with snow continuing to fall staff are facing an uphill battle to try and make sure that roads and pavements are kept clear."
In London, many councils sent gritting teams out on to the roads yesterday.
In Greenwich they started work at 7.30am yesterday and in Merton staff gritted the roads yesterday and twice again this morning.
More than 60 gritting lorries treated 1,890 miles of roads in Essex, while in North Tyneside workers used 150 tonnes of salt to grit 240 miles of road.
Motor insurer esure said it had received twice as many calls to register accident claims between 8am and 11am today as it did on a normal day, despite the fact that it estimates there is only around a third the usual level of traffic on the roads.
Adrian Webb, head of communications at esure, said: "This is a major weather incident and despite the warnings some people have clearly had to try to drive to work. Unfortunately, many of these have hit trouble early on.
"The situation has been made much worse because garages and rescue services are also overwhelmed too and they are having to make their way to broken-down cars in exactly the same terrible conditions."
In Gloucestershire, 57 schools closed this afternoon due to the chaotic weather, a number which rose sharply from the three announced this morning.
No roads are closed but the A4173 at Brookthorpe, the A4136 at Nailbridge and the B4008 at Quedgeley are described as "particularly icy".
A county council spokeswoman said between 5cm and 10cm of snow was likely with up to 30cm possible at higher ground.
One school is closed in South Gloucestershire - St Mary's in Yate.
The council has already deployed 4,000 tonnes of salt gritting the region's roads this year in the hope of averting tragedies.
Wiltshire county council said 39 county schools were closed by the afternoon due to the adverse weather conditions.
Two council roadshows promoting the new local government structure have been cancelled. They were due to take place in Corsham on Tuesday and Melksham on Wednesday.
In Somerset, five schools shut this afternoon as the snow began to fall, although no roads closed.
In Bristol, snow fell throughout the afternoon but just one school closed in the city, due to a heating fault that was not weather-related. No roads are reported blocked.
First Great Western trains advised against travel unless necessary, as services between Bristol Temple Meads and London Paddington are partly disrupted.
Bristol International Airport remained open today but the weather caused "some delays and a small number of cancellations", a spokesman said.
When snow covered the runway at 1.30pm, four incoming flights, from Milan, Krakow, Alicante and Dublin, were diverted to Bournemouth, Exeter and in the case of both Krakow and Dublin, to Cardiff.
A spokesman for the airport said Ryanair and easyJet were experiencing delays across their network which were affecting Bristol departures.
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