that sensor i believe is like outside cpu temp you could say, cause the internal temp of the cpu gets really really hot, but they base the "normal" temps on the mobo sensor and overheat temp, etc...cause if it overheats in the inside, then the overheat temp on the mobo will register as overheat too ;-)
My system temp rarely goes over 30 C but my CPU can get up to 38 C with water cooling. If you're using air I'd suspect temps anywhere from 45 C to 60 C depending on your setup.
The only way to truely know what temp your processor is at is to use one of the small digital thermometers from crazypc. Post a message to Hoot and he'll send you the instructions on how to do it. Very simple.