Britain faces a day of severe disruption as heavy snow, flooding and blizzard conditions blight the country.
Emergency services are already responding to a surge in weather-related call-outs, with government agencies issuing a string of warnings urging the public to take care on the roads.
More flooding is expected in the south-west as Thursday's heavy rain continues to pour throughout the day and overnight.
Snow is expected to blanket everywhere north of the M4 corridor, with up to 20cm (8in) hitting the worst-affected areas of north-west England, north Wales and south-west Scotland.
Higher areas could even see up to 40cm (16in) fall, while bitterly cold gale-force winds will sweep across Britain creating blizzard-like conditions and plunging temperatures down to well below freezing.
Heavy rain sweeping across Northern Ireland will turn increasingly to snow with up to 30cm (12in) across the hills of Down and Antrim, while on the east coast rain and sleet could cause localised flooding. The Police Service of Northern Ireland has already reported road closures because of stranded vehicles on the A8 near Newtownabbey.
James Wilby, a forecaster for Meteogroup, the weather division of the Press Association, said: "It is really just nasty conditions across most of the UK. The snow will fall from the M4 northwards, quite lightly in the south but heavily in the north.
"Along with the heavy rain and flooding in the south-west, there will no doubt be a lot of disruption for the UK today. The heavy rain, snow and strong winds will continue into the weekend, with the heavy snow spreading south to East Anglia and Bristol tomorrow.
"And I'm sorry to say that there is no sign of things getting any better next week. It's going to remain cold and bleak."
The Met Office has issued a number of severe weather warnings, urging the public to be prepared for "severe disruption" to transport and energy services. The Environment Agency has 18 flood alerts in place along the south-west coast warning of expected flooding, with a further 80 alerts issued to areas at risk.
Between 4cm and 6cm (1.6in-2.4in) is set to fall over southern Devon and Cornwall on Friday, and up to 10cm (4in) on exposed southern slopes.
On Thursday night, Cornwall council set up a designated control room to handle calls. A spokesman, Dave Owens, said the county's fire and rescue service had received more than 50 calls, and eight properties had flooded. "The main problem still appears to be surface water flooding which is continuing to affect a number of areas across Cornwall," he added.
There are reports of flooding across the west of the county, including around Newlyn and Penzance, as well as in Mevagissey in mid-Cornwall – a community still recovering from the impact of last year's torrential downpours.
The Environment Agency spokesman Ben Johnstone said: "We strongly urge people to sign up to flood warnings on the Environment Agency website, keep a close eye on local weather forecasts and be prepared for possible flooding. We also ask that people stay safe and not try to wade or drive through any deep water."
Darron Burness, the AA's head of special operations, said: "It's going to be a real witch's brew of driving wind, rain and snow, which will inevitably cause disruption on the roads. Drivers should be well prepared as even short journeys can quickly turn bad."
The Local Government Association said council gritting and ploughing teams would be out in force to try to ensure main roads remained passable where snow and freezing temperatures had been forecast.
Peter Box, chairman of the Local Government Association's economy and transport board, said hundreds of thousands of tonnes of salt had been spread this winter, but hundreds of thousands more tonnes were available in council depots and new deliveries were coming in.
Headded: "Council staff will be out and about over the next few days checking in on the people they know to be vulnerable and delivering hot meals and portable heaters, collecting prescriptions, defrosting pipes, fixing frozen boilers and making sure they have what they need." But he also urged residents with elderly or vulnerable family or neighbours to check in on them to make sure they were coping with the latest freeze.
Leeds Bradford international airport has suspended all flights due to "adverse weather conditions" and a number of schools have already closed across the Bradford, Derbyshire, Nottinghamshire and Huddersfield areas.