Hundreds of people have been urged to leave their homes in north Wales after a river surged over flood defences, as torrential rain fell across Britain for a seventh day.
"Although the weather forecast is improving, further property flooding and disruption is possible across the country as river and groundwater levels are set to peak in the next 48 hours"
- The Environment Agency
The Environment Agency warned the residents of 500 homes in the deluged city of St Asaph, north Wales, to evacuate after the River Elwy reached a record high on Tuesday.
Prime Minister David Cameron was set to visit flood-hit areas of southwest England, where two people have been killed since the storms began last Wednesday.
A man died in Somerset, southwest England, on Friday when he became trapped in his car in rising waters and a woman was killed by a falling tree in the city of Exeter.
Some 900 homes have been abandoned, while Britain's road and rail network have suffered days of chaos.
The Environment Agency has issued two severe flood warnings in Wales, including one in St Asaph, indicating a risk of death.
The agency said the city's River Elwy had reached a record level of 4.35 metres and was still rising over flood defences.
Water was waist-height in some parts of St Asaph, an AFP news agency photographer said.
Although it has a population of just 3,400, St Asaph was awarded city status this year to mark Queen Elizabeth II's diamond jubilee.
The Environment Agency said the rain was set to ease off in the next two days but warned that, with the ground already saturated, any further wet weather could prolong the chaos.
Nearly 200 flood warnings were still in place on Tuesday across north Wales, northeast England and the county of Northamptonshire in central England.
"Although the weather forecast is improving, further property flooding and disruption is possible across the country as river and groundwater levels are set to peak in the next 48 hours," the agency said.
Meanwhile, snow was expected to replace the rains in many coastal areas of Britain over the coming days.
The continued flooding risk comes after the Association of British Insurers said on Monday that hundreds of thousands of homes may be left without flood cover due to a row with ministers over how future flooding costs will be paid.
Environment minister Owen Paterson said the talks were ongoing.
Swathes of Britain were hit by floods in 2007, causing damage costing an estimated £3bn ($4.8bn, 3.7bn euros).