Forecasters are warning of a stormy end to 2012, with the year set to become the wettest on record in the UK.
The Environment Agency warned of more misery as a barrage of rain sweeps in, with the west of the country taking the brunt.
Many areas are still saturated after floods before Christmas. The agency has 84 flood warnings and 191 flood alerts in place, with the Midlands and south-east worst affected.
In London, the Thames Barrier was raised on Thursday morning for the first time since March 2010, to reduce the risk of flooding as water from days of downpours causes high levels further upstream. It will be raised again on Friday morning.
A storm brewing in the Atlantic could bring up to two inches (50mm) of rain and 80mph winds in some areas this weekend.
Provisional figures show that 1.8in (46mm) of rain is needed between 27 and 31 December for 2012 to be the wettest year on record for the UK.
A new record has already been set for England, with 43.1in (1,095.8mm) falling between 1 January and Boxing Day, the Met Office said.
New regional rainfall records have been set in several areas of England, including the north (49.3in), east and north-east (41in), the Midlands (41.3in), and East Anglia (31in).
An Environment Agency spokeswoman said: “The weather is set to remain unsettled into the weekend. With the ground still very wet and river levels running high, any rain is likely to increase the risk of flooding.
“There is also an ongoing risk of flooding from groundwater, particularly in Dorset, and some larger rivers like the Thames and Severn are still rising as they slowly respond to the recent downpours. As a result we may see further flooding of low-lying land, such as flood plains and low-lying roads, as the peak in river levels moves downstream.”
Friday night and the early hours of Saturday morning are likely to see the worst of the stormy weather, with wind speeds reaching 80mph in areas including north-east Scotland and the Western Isles. More showers will arrive over western Britain and Northern Ireland on Sunday.
The British Geological Survey has an amber landslide warning in place for the south-west and is urging walkers to take care along coastal routes.
Lightning is believed to have started blazes at Lytchett Minster school, and the derelict Cliff House Hotel, a few miles from each other in Bournemouth, Dorset.
The heavy rain and late-running engineering works meant a miserable return to work for many rail travellers on Thursday.
First Great Western said the main line in the south-west, which has been closed since before Christmas because of flooding between Exeter St Davids and Tiverton, was expected to reopen on Saturday.
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