CD ripping temperatures


I'm running a PB G4 12" 1.5 GHz. When importing a CD in itunes, the processor gets up to about 138 degrees F (normally it hovers around 108-110). I understand that copying CDs is pretty processor intensive, but that seems a little hot to me. How hot is it safe for these machines to get?
How do you measure the temperature? Didn't know it was possible to access the G4 temperature sensor via software. 138 degrees F would be 58°C. This doesn't sound that much. Does your fan start spinning loudly while you are ripping a CD?
I use a program called Temperature Monitor (a web search should find it pretty easily). The fan doesn't come on as fast as it can, but at around 140 F (~60 C) the G4 is starting to approach the temperature of my other machine, which is a 3 GHz Pentium 4 Prescott, and those run really hot.

It seems a little high to me, but do these sound like problem temperatures to anyone else?