Before this, what was the reading of your temperature?
Also, after you run the games that you mentioned, the GPU idles at 40-45C?
What was your idle temp before? Just roughly

I would suggest you install 3rd party coolers
Other than that, I can't seem to find the problem of that happening

Maybe something changed with your GPU settings, accidentally
Either in game or desktop
Logically that is the only explanation I can think of

I think you need to change the cooling system overall
Try get a 3rd party cooler for the GPU or water cooling
The card is operating at a very dangerous temperature, which risk degrading the components inside the card

Before I go further, just wanna ask something
Your GPU design is the reference design? The blower one?
Or using 2/3 fans?

I see, reference design is known to have cooling issue, because of a single blower setup
The only way I can think of is to remove the cooler altogether, and replace it with a aftermarket 3 fans
Seems like a lot of hassle to do so
I am not sure how to help with this

Eureka! This was the cooler I saw. Definitely get this for better cooling THE ZUL
Also, need to take into considerations what goldfries have suggested
Might be contributing factors towards excessive heat

Nah, unless you are overclocking, stressing the CPU to near full load, voltage should be lower than advertised