A substrate processing system includes a processing chamber, a pedestal for supporting a substrate disposed within the processing chamber, and an optical pyrometry assembly coupled to the processing chamber to measure an emitted light originating substantially from a portion of the pedestal or substrate. The optical pyrometry assembly further includes a light receiver, and an optical detector. The optical pyrometry assembly receives a portion of the emitted light, and a temperature of the substrate is determined from an intensity of the portion of the emitted light near at least one wavelength.