Mirror mounting with integral rain gutter

A mirror assembly has a housing that houses a mirrored reflecting surface for enabling a person in a driver's compartment of a vehicle cab to look through a side door window opening and see a field of view toward the rear of the vehicle. The mirror assembly mounting includes a mounting bar that is attached to the side door, that has a length running along the top margin of the door, and that along at least a portion of that length comprises an upwardly open channel for collecting rainwater runoff from the roof and carrying it rearward before the runoff can wash across the window opening.