A temperature controlled dielectric window of an inductively coupled plasma processing chamber includes a dielectric window forming a top wall of the plasma processing chamber having at least first and second channels therein. A liquid circulating system includes a source of cold liquid circulating in a first closed loop which is not in fluid communication with the channels, a source of hot liquid circulating in a second closed loop which is in fluid communication with the channels, and first and second heat exchangers. The cold liquid passes through the first heat exchanger at a controllable flow rate and temperature of the hot liquid is adjusted by heat exchange with the cold liquid as the hot liquid passes through the first heat exchanger and then through the inlet of the first channel. The cold liquid passes through the second heat exchanger at a controllable flow rate and temperature of the hot liquid is adjusted by heat exchange with the cold liquid as the hot liquid passes through the second heat exchanger and then through the inlet of the second channel.