Well you hve written several things which tell me why your having problems.
You siad it was HOT in there. Your CPU can only operate at or above ambeitn temp. And that would be with a watercooling kit capable of droopinh the temp near ambeint.
Then you said "dust off" which tells me your HSF may in fact be so caked with dust it's simply not able to do its job, and in most cases you can't see the extent of the dust.
Resolve:
open your PC case and leave the side panels off. This should get it closer to ambeint temp.
remove your HSF and thoroughly clean it. clean you CPU with isopropyl alcohol the higher the percentage the better for example 90%, don't go lower then 80% IMHO.
Opening your case up and removing the side panels will probably drop temps immediatly.