Abstract: Embodiments are disclosed of a radiator temperature control apparatus for controlling the heat output of a radiator. The radiator temperature control apparatus may include an airtight enclosure around the air outlet of the radiator air vent, an adjustable opening in the airtight enclosure controlled by an actuator, and a controller connected to the actuator. In operation, the controller can be configured to open the adjustable opening in the airtight enclosure allowing air in the radiator to be expelled through the adjustable opening, thereby allowing steam to enter the radiator, and heat the room. The controller can be configured to close the adjustable opening, stopping air from being expelled from the radiator, thereby stopping additional steam from entering the radiator.