THE Environment Agency has issued a flood alert for the River Calder and its tributaries from Todmorden to Hebden Bridge.
An intense band of rain will cross the area from the east through Friday.
Most of the rain is expected to fall between 6am and 6pm.
“We are currently forecasting rainfall totals of between 40 and 60 millimetres and up to 50 millimetres in places.
“This could cause surface water problems and river levels to rise. We are expecting to issue a number of flood warnings through Friday morning,” said a spokesman.