More than 800 homes and businesses were flooded in Cornwall, Devon, Gloucestershire and Worcestershire counties, the British newspaper the Guardian reported Monday.
The government meteorological department, known as the Met Office, has warned 40 to 70 millimeters (1.57 to 2.75 inches) of rain is expected to fall further north.
Met Office chief forecaster Eddy Carroll said the heaviest "is expected to be over parts of northern England and North Wales."
Prime Minister David Cameron promised to help communities mopping up after a month of rain fell in four days, the newspaper said.
The government Environment Agency said most new flood defense systems, installed after flooding in 2007, were working well, but one of two large pumps installed in the village of Kempsey, part of a million-pound ($1.6 million) project, failed, and water from an overflowing brook poured into homes.