I have no idea what that particular cpu's nominal or safe temperature is. But I can tell you that I did this little test- I put my finger in a cup of hot water after measuring the temperature with a thermometer(the type you put in your mouth when you are sick)at 50c and it burned my finger in 25 seconds I had to take my finger out with burn reaction. Then I tried again with the water at 49 celcius and I could keep my finger in there forever no problem without feeling burned lol.
Regarding my Intel P4 (Northwood) i've read people say under 50c and then some would say 55c and other would say 60c heh I go with 49c max for mine because whenever my 2.6 Intel P4 would reach 50c it would error. But all cpu thresholds are different.
Lighters and aerosol cans also have warnings that say do not expose to heat above 49c lol so there definetaly is some good heat there at 50c. But all cpu's are different. Sorry I could'nt give you a straight answer.