A yellow weather warning for heavy rain has been put in place for Devon across Thursday.
The weather warning is in place from 11:00 GMT to 23:59 on Thursday.
Devon County Council's highways team urged motorists to "drive to conditions" as flooding and travel disruption was expected.
The Met Office said the alert included Cornwall and parts of Somerset, Bristol and Gloucestershire.
The Met Office said about 15 to 20mm of rain was expected to fall widely and 30 to 40mm was likely over higher ground.