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.