The flood watch means people should keep an eye on rising river levels and be ready to act quickly if flooding starts.
Meteorologist Johnny Burg with the National Weather Service says heavy rains are expected to bring the Nooksack River to just above flood stage in Ferndale this evening.
That's expected to cause minor flooding in low lying farm lands and roadways.
Rain in the lowlands could also cause street flooding in urban areas with poor drainage.
Residents are reminded to keep storm drains clear of any leaves or debris, and not to drive through flooded streets.