a vehicular rain sensor which senses precipitation at a vehicle window . the rain sensor comprises an imaging array sensor and a control . the imaging array sensor is directed at the vehicle window from inside the vehicle and comprises a camera device capable of imaging precipitation at a surface of the window . the camera is operable to image the precipitation at least in response to ambient light present at the window . the control responds to an output of the imaging array sensor in order to indicate precipitation at the surface of the window . the control determines the presence of precipitation via spatial filtering of the image received by the camera device .