An electrical rain sensor to be mounted on the outside of the main frame of an openable window, particularly a skylight, comprising a sensing element with two electrodes mounted opposite one another in an insulating holder, the distance between the electrodes being less than the size of a raindrop. To the electrodes an electric circuit is connected which by detection of a change in an electrical quantity caused by the presence of raindrops, activates a maneuvering device which closes the window. The holder (8) is produced by moulding of an electrically insulating thermoplastic, wherein the supply lines to the electrodes (15, 16) as well as a heating element for the drying of the sensor is produced as inserts in the holder by moulding of an electrically conductive thermoplastic polymer into excavated recesses and/or grooves in the holder (8). The electrodes can be designed as coatings of a weather resistant conducting material, particularly material containing graphite, the conducting material being applied to most of the surface of the sensor.