An interior rearview mirror system suitable for use in a vehicle includes a interior rearview mirror assembly adapted for attachment to an interior portion of the vehicle. The interior rearview mirror assembly includes a housing and a reflective element included within the housing. The mirror system further includes a video device (which includes an imaging sensor) and a control. The imaging sensor is positioned at the interior rearview mirror assembly and has a field of view forward and through the windshield. The imaging sensor is operable to at least sense precipitation at an interior and/or exterior surface of the windshield. The control receives a signal from the imaging sensor and is operable to control at least one of a headlamp of the vehicle, a windshield wiper of the vehicle, a defogging system of the vehicle and a movable window of the vehicle in response to the signal.