I have an NUC5I5RYH, it sit on my desk with no source of heat around. Room temp. is around 22 °C or 72 °F.
AIDA64 - ver. 5.20.3400 build date 23.03.2015 report CPU core - 50 °C - 122 °F in idle. I think is too much ! After couple of minutes of System Stability Test CPU core temp hit 86-88 °C - 190°F
Please post your CPU temp. because I think I have a thermal problem with my NUC.
I have the last BIOS vers. and the cooling settings in BIOS is on default - balanced.