Powerful winds and two weeks of rain in 24 hours will make Friday particularly difficult for drivers, according to forecasters.
Localised flooding and winds gusting to 50mph will make it a "thoroughly miserable" day, according Paul Mott of MeteoGroup, who advised commuters to leave extra time for their journeys.
After battering south-west England and south Wales, the rain is expected to head north east throughout the day, hitting Northern Ireland and the south of Scotland by mid-afternoon.
Mr Mott said: "There will be some localised flooding in Wales and the north east in areas that are prone to it, but we're not expecting widespread flooding.
"It's going to remain unstable over the weekend. There will be rain, sometimes heavy rain, through the UK, with northern England bearing the brunt of it."
People in Gloucestershire are bracing themselves for another night of heavy rain after storms swept into the region, causing flash floods. Downpours overnight and Friday morning have led to road closures in the county, and firefighters had to pump out floodwater from homes.
The Met Office has issued a severe weather warning for the region until Friday evening, and said around 2in of rain is expected.
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