Just how hot is Coffee Lake?
 

Intel's Core i7-8700K has proved to be an exceptionally well-rounded CPU in our testing so far, but one potential negative has come up again and again in the other reviews I've been reading. Many reviewers have noted that the chip "runs hot," so much so that the idea even made for sub-headline news at one outlet. I was a bit confused reading these statements, because the i7-8700K didn't seem to be an exceptionally hot-running chip in my testing compared to other modern Intel CPUs. Although I ran into a thermal limit while trying to boost voltages enough to get our chip stable under a Prime95 AVX workload, running all of the chip's AVX units at 4.8 GHz was no small feat, and we expect high temperatures as a matter of course from unmodified Intel CPUs when they're overclocked.

http://techreport.com/blog/32661/jus...is-coffee-lake