CPU temp jumps

[Legend]

Is this normal? I've checked in Core Temp and Hardware Monitor and it's doing the same thing. Just at idle it will be 16-19 degrees, then suddenly jump to 36-40, then back down again, and keeps doing it on all the cores randomly, but they never do it unison, it's just one or two at a time, very erratic. The min/max for all cores are within 2 degrees of each other, but I don't recall seeing this before.

It's a 6700K (not OC'd yet) with EK Supremacy block and TG Kryonaut.

 

[Legend]

Yes but there is no load... literally doing nothing on a fresh boot in to Windows, even when I shut down all non-essential background processes.

I'm wondering if the block just needs to be tightened?

 

[Legend]

OK, well I've been reading online this is hardly uncommon, so it doesn't seem I have a need for worry. Max temps certainly aren't bad at all, and all cores are even in that respect.