A method of in-situ temperature measurement for a wafer treatment reactor such as a chemical vapor deposition reactor desirably includes the steps of heating the reactor until the reactor reaches a wafer treatment temperature and rotating a wafer support element within the reactor about a rotational axis. The method desirably further includes, while the wafer support element is rotating about the rotational axis, obtaining first operating temperature measurements using a first operating pyrometer that receives radiation from a first portion of the wafer support element, and obtaining first wafer temperature measurements using a wafer temperature measurement device that receives radiation from at least one wafer, the wafer temperature measurement device located at a first position.