A rain sensor for an automotive wiper control system detects rain conditions to produce a rain condition indicative signal. The rain sensor includes a vibrator, the outer surface of which is exposed to rain drops and which vibrates or oscillates at an amplitude and frequency corresponding to the energy applied by rain drops. The rain sensor is adapted to produce the rain condition indicative signals corresponding to the vibration amplitude of the vibrator. The vibrator is resiliently suspended within a sensor casing by means of a resilient member which is adapted to allow vibration of the vibrator as rain drops hit the outer surface and to absorb vibrational noises transmitted through the vehicle body. The resilent member simultaneously serves to waterproof the components within the sensor casing.