A CPU that is idling should be somewhere near 30c to 40c. Working hard, they can get to 55c to 65c without any problems. And if you have a good, solid CPU cooler, its going to stay in those ranges for the most part. You might see an occasional 70c, maybe even 75c. Once you get to 80c I start trying to figure out why my CPU is that warm, and if I see 90c or higher I power-down.
You probably will not do any damage to your CPU until you get past 100c, but I for one do not like taking chances with multi-hundred dollar items.
90c is 194f. Pretty damned warm.
100c is 212f. Thats getting hot.