I have found this reading under Debug in version 2.3 on the Canon T2i to be unreliable. The temperature reading did not budge above room temperature (23C) after 45 minutes of recording even though at this point the overheating icon appeared. I continued to record for another 15 or 20 minutes and the camera still did not shut down. At that point my batteries happened to run out, though. It took me around a minute or two to switch to new batteries in the grip and turn the camera back on to resume recording. I then checked the Debug screen again and it was now suddenly showing ten degrees higher at 33C. I have no idea how much higher than this the temperature may have been before the overheating icon appeared or before my batteries went dead. I had been hoping the CMOS temperature reading might have been useful for me to keep an eye on to get an idea when to anticipate the overheating warning. About the only thing I can go by now is the 45 minute mark or less if ambient temperatures are higher. Any comments would be much appreciated.