(CNN) -- Days of heavy rain have led to flooding in southwestern England and parts of Wales and at least one fatality, British authorities said Sunday.

The UK Environment Agency posted a severe flood alert for the town of Helston, in the southwestern county of Cornwall, where the River Cober was rising over its banks, and warned towns across England and Wales to prepare for more high water. In Exeter, in neighboring Devon, a woman was killed when a tree fell on her Saturday night, the Devon and Cornwall Police Service reported. 

On Twitter, Prime Minister David Cameron called the scenes of flooding "shocking" and said his government would make sure "everything is being done to help." 

The region has seen four days of non-stop rainfall that has capped months of heavy precipitation, including the wettest April-June period on record. More than 225 areas stretching from Cornwall through the Midlands region to the northeastern coast were under flood warnings Sunday afternoon as the latest system moved through, the Environment Agency said. 

CNN's Susannah Palk and Matt Smith contributed to this report.

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