Motorists have been warned against driving in some areas as heavy rain hit the South West and forecasters said snow could cause widespread disruption further north.
The Met Office has issued a cold weather amber alert – the second highest warning on its scale – as rain, sleet and snow, coupled with strong winds, spread from the South West.
Up to 60mm of rain is expected in some areas, according to the Met Office.
Seventy-nine flood alerts , meaning flooding is possible, are in place as well as eight flood warnings, meaning it is likely.
Police in the South West said they had already received a “significant” surge in call-outs on Thursday evening.
Sgt Dave Opara, based in Plymouth, said: “There has been a considerable amount of rainfall across the force area.
“There will be more to come throughout the night, so the situation is not going to get much better too soon.”
Cornwall opened its dedicated control centre to deal with the volume of calls about flooding. Fire crews had already been called out to 50 incidents before 10pm on Thursday.
Newlyn, in the southwest of the county, was reported to be the worst affected area.
Sky’s Mark White said: “In Newlyn, a number of properties are underwater.
“The emergency servcies are doing their best to pump out these flooded properties and keep the roads clear but it is very bad at the moment and it is continuing to move east.”
Environment Agency spokesperson Pete Fox said: “Heavy rain in southwest England and south Wales on Thursday and into Friday means there is a risk of localised surface water and river flooding in the south west, the southern counties and parts of south Wales.
“The public can sign up for flood warnings and check the latest information on the Environment Agency’s website , or follow us on Twitter at @EnvAgency.”
Sky News weather producer Joanna Robinson said: “March can be a month of extremes and that’s certainly what we’re seeing this year.
“The cold theme is set to continue, with disruptive snow across parts of the UK.
“Over the next 24 hours, central parts of the UK will be most at risk of significant snow, particularly Northern Ireland, southwest Scotland, northwest England, northeast Wales and the north Midlands.
“There will be drifting in the raw wind and blizzard conditions. Disruption is likely to transport and perhaps even power supplies.”
In the South West, an amber alert for heavy rain was been issued for Friday and Saturday, warning of localised flooding and travel problems, while amber snow warnings have been issued for Northern Ireland, the North West and the West Midlands.
Darron Burness, head of the AA’s Special Operations Response Team , 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.
“Drifting snow could repeat the scenes we saw in southern England last week when hundreds of drivers got stuck overnight – it only takes one or two vehicles struggling for grip for the situation to quickly escalate.
“Keep your speed down as visibility could be seriously reduced and there’s a risk of localised flooding – just stay out of flood water.
“Also with temperatures set to remain low, any snow that settles will likely persist for several days, so be wary of icy patches.
“Wherever you’re going, take plenty of warm layers, check the travel reports before heading out and stick to the main roads where possible.”
The Local Government Association said council gritting and ploughing teams would be out in force to try to ensure main roads remained passable.