Abstract: A method for warming the rotor of a gas turbine during extended periods of downtime comprising feeding ambient air to an air blower; extracting compressed air from the air blower; feeding a portion of the compressed air to one side of a heat exchanger and steam (typically saturated) from e.g. a gas turbine heat recovery steam generator; passing the resulting heated air stream from the exchanger into and through into defined flow channels formed within the rotor; continuously monitoring the air temperature inside the rotor; and controlling the amount of air and steam fed to the heat exchanger using a feedback control loop that controls the amount of air and steam feeds to the exchanger and/or adjusts the flow rate of heated air stream into the rotor.