Britain is facing a Christmas Day freeze as mild, stormy conditions give way to Arctic temperatures and some festive snow on higher ground.
A cold northerly blast will roar in during the middle of next week with wintry showers possible on the big day.
It will follow an unsettled weekend with bouts of strong winds and torrential forecast through until Christmas Eve.
Heavy rain threatens flooding across swathes of Britain prompting a raft of Met Officeweather warnings and Environment Agency alerts.
A severe weather warning for more heavy rain is in place across southern England from 12.01am on Saturday until noon on Sunday.
It warns of potential travel delays and flooding as up to 30mm of rain is forecast in parts during the warning period.
It means those heading home for Christmas could face severe delays.
Thermometers will plunge overnight into Christmas morning with a widespread frost expected and slim chance of snow.
James Madden, forecaster for Exacta Weather, said: "We could still see a true White Christmas particularly in northern parts of the country."
A blast of air from the south will push temperatures above-average for winter over the next few days.
Low-pressure from the west will give the weather a shake up with heavy rain threatening floods in parts of the country.
The weather will start to calm down towards the middle of next week when polar air will make it feel much colder.
Met Office meteorologist Emma Smith said: "We are going into quite an unsettled period of weather with low pressure in charge although it will feel milder in the run up to Christmas.
"After the weekend high pressure will build and although it will be more settled it will turn colder with the arrival of Arctic Maritime air.
"There will be some showers around on Christmas Eve although Christmas Day is looking drier.
"There will be some easterly winds along the east coast of the country, to the southwest there will be milder winds coming in from the west."
Weather Company meteorologist Amy Hodgson added: "Our current forecast favours slightly cooler conditions from Christmas Day, with temperatures dropping marginally below normal as a colder flow from the north-east develops across eastern areas."
On Friday, adverse weather led to the part-closure of the M23 motorway while several rail lines were blocked.
Sussex Police described driving conditions in the region as "miserable", and said there was "a lot of standing water on the roads".
Devon and Cornwall Police said flooding across the force area made "a number of roads impassable" and it urged motorists to take extra care and avoid driving into standing water.
Highways England has urged motorists to adapt their driving for wet weather by slowing down, keeping well back from the vehicle in front and easing off the accelerator if steering becomes unresponsive.
John Halsall, managing director of Network Rail's southern region, said the combination of one of the wettest autumns since records began with a month's worth of rainfall in the past five days has put the rail network "under enormous pressure".
Southern, Thameslink and Gatwick Express services were affected after rail lines were flooded.