p111 temp

32-42 degrees celsius at idle and 42- 52 degrees celsius at full load is in the safe range. the lower the better. check your motherboard temp. if it is more than a few degrees celsius warmer than the air in the room, you need better case cooling.
 
The cpu can take quite a bit more heat than that, but the stable area is where Rick said. Around the mid to upper 60's, you'll probably start getting errors/lockups.