Out of curiosity, I wanted to know exactly how hot the Geforce 6600 GT in my desktop PC here was. Turns out, it idles about 52 Celsius (125 F).
Then, again, out of curiosity, I put it under some load, by running glxgears at full screen – 1600×1200. Turns out the GPU positively roasts at such a temperature.
83 C ~= 181 F.