Strom Christoph is set to bring widespread flooding, gales and snow to parts Wales.
There are yellow warnings for rain in place across the whole of Wales for the next three days (Tuesday to Thursday) and a major incident has been declared in South Yorkshire.
People there are being urged to prepare as an amber weather warning for rain was issued by the Met Office for Tuesday to Thursday for central northern England, affecting an area around Manchester, Leeds and Sheffield and stretching down to Peterborough.
It has led to a major incident being declared in South Yorkshire in preparation for potential flooding, said Ros Jones, mayor of Doncaster.
Heavy rain is expected to hit the UK overnight on Tuesday, with the Met Office warning homes and businesses are likely to be flooded, causing damage to some buildings.
It issued a "danger to life" warning due to fast-flowing or deep floodwater, while there is a "good chance" some communities may be cut off by flooded roads.
The warning states: "Several days of persistent, and occasionally heavy, rain are expected to affect the region as Storm Christoph affects the UK.
"The heaviest and most persistent rain is likely to be across Wales and the high ground of northern England.
"By early Thursday, 30-60 mm of rain is expected to have fallen widely across the warning area, with 100-150 mm over the high ground of Wales and northern England.
"Up to 200 mm is possible across parts of north Wales and northwest England.
Up to 70mm is expected to fall but in isolated spots, particularly in northern parts of Wales, 200mm could be possible.
Welsh forecaster Sue Charles said: "Storm Chrisoph will bring heavy rain and gale force winds today (Tuesday) and tomorrow (Wednesday). Warnings in place. Rain likely to be heaviest in Snowdonia (200mm possible) with an ongoing risk of flooding."
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