Residents in Cleckheaton, Liversedge, Birstall and Dewsbury are warned to prepare for possible flooding as heavy rain is expected to cause river levels to rise.
The Environment Agency has issued a flood alert for the River Spen and Batley Beck catchments, which include the Blacup Beck, Lands Beck and Canker Dyke.
The alert means that flooding of low lying land near watercourses is possible from the early hours of Friday, 20 October.
The agency said that further heavy rainfall is forecast throughout the weekend and river levels are expected to continue to rise.
It advised people to avoid using low lying footpaths and bridges near local watercourses and not to attempt to walk or drive through flood water.
It also urged residents and businesses to start acting on their flood plan if they have one, or to create one if they do not.
The agency said it has opened its incident rooms and is closely monitoring rainfall and river levels.
It said it will update the message by 09:00 AM on 20 October, or as the situation changes