Anything below 120°C is childs play :P
In seriousness though: What CPU do you have? 84°C should be fine but some cores were maybe already scaling down.
Depends on the CPU.
In saying that, there isn't any risk to your system, CPU's will thermal throttle before they incur any damage... That technology has existed since the Pentium 4 with Intel, Athlon 64 with AMD.
Also... Again, depending on your CPU you may actually need to set an offset, so your temperatures may have been higher or lower than 84'C... I.E. The old AMD Phenom 2's had a 13'C offset, so if you hit 60'C you were actually 73'C.
Hmmm. What's the offset for a 3700X?
I might finally get around to plugging the custom fan controllers in that my PC case came with. That way I can control my intake and outtake fan speeds with the front panel knobs that are on my case. Right now the fans are all just powered by the mobo fan plugs ins.
Is there any way to get a history of your CPU temps? That way you can see how long you were at your highest temp?
Thanks for the info and the help BTW.