A solenoid valve for controlling a hydraulic system having a coil which is composed of an electrical conductor, an armature which is situated at least partially inside the coil and is connected to a valve element for opening and closing a flow opening of the solenoid valve, and a hydraulic fluid-filled valve chamber that accommodates the armature and communicates fluidically with the hydraulic system. The armature is supported in movable fashion in the hydraulic fluid of the hydraulic system. In order to reduce the viscosity of the hydraulic fluid, the coil is situated so that a heating of the coil produced by a current flow produces a heating of the hydraulic fluid in the valve chamber.