A thermostat mixing valve for a water temperature control system may comprise a mixing chamber defining a valve outlet, a first proportional solenoid valve fluidly coupled to the mixing chamber, and a second proportional solenoid valve fluidly coupled to the mixing chamber. Each of the first proportional solenoid valve and the second proportional solenoid valve may include a housing assembly defining a fluid inlet and a fluid outlet, a plunger assembly configured to translate relative to the housing assembly, and a coil assembly configured to generate a magnetic field that translates the plunger assembly.