At what point should I worry about my iMac overheating?

Don’t worry about it. There’s a thermal safety shutdown in the firmware. Also, the newer Core Duo chips will happily run up to 80C without blinking. Have a cool drink and relax.

Thanks.. Unfortunately my cool drink will only be cool for about ten minutes. It is good to know the computer will shut itself down if it gets too hot.

I would have it checked out if it shuts itself off regularly. It shouldn’t be running that hot – might be a fault in the powersupply and/or trigger for the cooling system.

160F (71C) is well within the safe operating temperature. The computer will hard shutdown if it reaches a critical temperature, although it is very unlikely to ever get to this point. The fans and natural heat dissipation inside the computer are very well managed; if you feel the vent at the top of the back, it will often be venting much of the internal heat without the fans having to do anything more than idle.

As the core reaches critical temperature, the internal fans will be running at maximum speed, and the computer will cause all processes to run slowly in order to allow the processor to cool. If the processor temperature continues to rise, the computer will shut off completely.

Your computer should be fine JP. If things suddenly slow down like hell, then it might be time to wonder if there’s something wrong with the fans perhaps. Oh, and I’m jealous of the weather you guys are having!