Anne Bartlett and her dog Henry look out from their flooded property in Somerset, England, on Sunday.

Story highlights

NEW: More rain, flooding forecast for Sunday

Flood alerts posted across England and Wales after days of rain

A falling tree kills a woman in southwestern England

Cameron pledges help for the stricken region

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.

The Environment Agency said more than 800 properties have flooded since Wednesday. And the Met Office, the UK’s national weather service, said more rain is forecast for the area – but the wettest weather will be in the north.

“We can expect between 30 and 40 millimeters (1 1/4 to 1 1/2 inches) of rain falling in many areas and up to 70 millimeters (2 3/4 inches) of rain in parts of northeast England, continuing the risk of further flooding and travel disruption,” forecaster Eddy Carroll said in a news release.

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.

Officials warned residents to use the daylight to prepare for more flooding Sunday and into the early hours of Monday.

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