Mates, I have a problem with AMD athlon x4 860k. Idle temperature is something like 66 (bios shows that temperature), under stress (playing rust) hwmonitor shows even more than 100C. Well probably it's not that bad, because computer should restart with that temperatures however i have some fps drops while playing rust, it's worrying. My motherboard is ASRock FM2A58M-DG3+. Standard cooler has been replaced with arctic freezer 7 and, thermal paste i used is Arctic Silver 5, unfortunetaly it doesnt help.
Unless your case airflow is nil and ambient temperatures are north of 40°C, then it's a faulty thermal sensor and should be ignored. Rust is still in alpha development, so you should expect issues.