When I first got Skyrim, it was running on my GT 545 at almost 100 C even at medium setting. Way too high. So I have used Nvidia Inspector to set global FPS to 30, and then set the FPS for Skyrim so the temperature does not go above 80.
That is generally OK for open scenery, but results in quite a bit of graphic lag in dungeons.
I could raise the max temperature to 85, but is i really OK to run for prolongued periods at that sort of temperature ? I'm certainly not going as high as 90.