Dozens of flood alerts are in place as driving rain and winds of up to 80mph sweep across the country, bringing chaos for Christmas travellers.
The stormy weather started this morning in the South West and is moving eastwards and northwards as the day continues.
Almost all of the UK will be affected by the relentless rain falling on already saturated ground and winds whipping to 70-80mph in eastern and central areas through this afternoon and overnight.
Around 3,000 homes are without power in Cornwall and a further 2,000 in other parts of the South West after high winds brought down power lines, according to Western Power Distribution. According to Southern Electricity, there are 1,100 without power in Berkshire.
In Cumbria, police, the RAF and mountain rescue teams are searching for a man who is believed to have fallen into the River Rothay at Ambleside.
Most of the country will see rain at some point
In Horsham, West Sussex, two children were treated for minor injuries after being hit by branches from a falling tree.
The spokesman for the Met Office said a new wind speed high had been recorded at Capel Curig in Conwy, North Wales, with gusts blowing at 87mph.
Not far behind was Berry Head in Torbay, Devon, with gusts of 76mph.
The Dartford QE2 bridge is closed until 4am tomorrow morning, the M48 Severn Bridge is closed to high-sided vehicles and the Sheppey Crossing in Kent has been closed.
An Essex police spokesman said: "The tunnels will remain open to help maintain the flow of traffic, but congestion is expected so drivers are advised to seek alternative routes if possible or avoid the Thurrock and Dartford areas of Essex and Kent."
The Met Office has issued more than 130 amber "be prepared" warnings for London, southeast and southwest England, and South Wales.
A roof blew off a property in Hatherleigh, Devon. Pic: @Orchella49
Eight areas, including four in the South West, have been issued with "immediate action required" flood warnings.
Localised flooding is possible and winds of 50-60mph are forecast in inland areas, gusting up to 80mph along the coast.
Sky News' weather presenter Nazaneen Ghaffar said rain would be the biggest problem for most people today.
"There will be heavy downpours bringing 20-40mm of rainfall quite widely and over 60mm likely across parts of the high ground.
"As the rain is falling on already saturated ground that could cause both surface water and river flooding in these areas."
More than 100 'be prepared' alerts have been issued
:: See the latest weather forecast here
But it is the trains that are expected to bear the brunt of the nasty weather and at least 21 train companies are predicting changes to timetables and cancelled services.
An emergency go-slow limit of 50mph is likely on many routes.
Train bosses say "hundreds of engineers" will be on call over the next two days to deal with any blocked tracks or technical problems.
Passengers are being urged to check the latest information before setting out.
Network Rail Managing Director Robin Gisby said: "I want to be very clear that our priority is running as many trains as we can safely, rather than worrying about hitting the timetable bang on."
Virgin Trains is one of many operators warning of delays and disruption
Many companies have removed limits on day tickets to deter people from travelling at the height of the bad weather.
Virgin Trains is advising passengers to travel before 3pm and says advance tickets for specific trains will be accepted on any service.
It says fewer trains than normal will run between London and Manchester, and London and Birmingham - where the 50mph limit is likely to be enforced.
South West Trains is another operator warning of "significantly reduced speeds" on its network.
Motorists are also being urged to be take special care on the roads and check the flood updates ahead of their journey, as the AA reported it was dealing with 1,100 breakdowns every hour.
The A82 in Scotland, where there is an ice alert. Pic: @pressscotland
The Environment Agency and the AA strongly advise not entering flood water that is moving or more than 10cm deep.
David Jordan, Director of Operations at the Environment Agency, said: "Tragically people die because they've taken risks and attempted to drive through flood water just to save a few minutes.
"Flood water is dangerous. If there is widespread flooding in your area then don't travel and if a road is closed then turn around and make a detour."
The Highways Agency said high-sided vehicles and motorcyclists should be especially careful in the high winds and and has put out a list of potentially treacherous routes.
John McTaggart, head of on-road services at the agency, said: "We are working closely with the Met Office to monitor conditions.
"In the event of persistent high winds we may need to close certain bridges to traffic for a period, so please be alert for warnings of closures and follow the clearly signed diversion routes."
The RAC is predicting that 13 million people will take to the roads from December 24 to 26.
Thirty flights have been cancelled from Heathrow Airport.
Visitor attractions are also playing it safe, with the popular Winter Wonderland in London's Hyde Park staying shut on Monday as well as Kew Gardens' Christmas attraction.
Festive revellers will get a brief respite from the unsettled weather on Christmas Day and Boxing Day but the stormy conditions are due to return on Friday.
In Brighton, the council announced that the traditional Christmas Day dip would be cancelled because of the severe weather conditions.
The swim, which was also stopped last year because of dangerous weather conditions, has been running since 1860 and usually attracts scores of participants.
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