Theomv:
Although your code makes much much much more sense, i dont think it adresses the issue of the temperature spikes
I just think he's trying to point out a subtle bug in your code.
Personally I'd make a copy of your code and rip out all the servo stuff and focus on the temperature code. Add some extra serial.print's for the intermediate calculations so you can focus on what's going wrong.
Once you've got rock solid temperature readings you then add back in the servo code.
Just a thought.
Regards,
Brad
KF7FER