I bet you didn't clean the inards of your comp FOR A LONG TIME. Well for your notice dust bunnies may be clogging up your precious hardware and also increasing the overall temperature. Do know that you must clean your comp at least 2 times a year.
So my advice: FRIKIN CLEAN YOUR COMPUTER.
Don't forget to shrub old termal paste (termopasta) off your processor and heatsink and apply a new layer of it.
Also please post your temperate readings before doing the clean-up action.
YouTube has many how-to videos on how to clean your comp - use them as a refference. But also take a snip to a texted information on this matter.
P.S.: Never delay computer clean-up. If not taken at time it may cost you more than you expect.