Some sensors can report temps that are way off, nothing to worry about as long as the CPU is within acceptable limits. From what I have heard, AMD boards are particularly bad at reporting correct information.
What equipment do you have, and are your CPU temps good?
i5 4440, Sapphire R9 290, a Corsair Spec-02 case, two 140 mm x 25 mm front intake fans, one 120 mm x 15 mm bottom intake fan, one rear 120 mm x 25 mm exhaust fan, and two top 120 mm x 25 mm exhaust fans.
CPU temp is around 30 C idle and upper 50's C when overload. Also GPU temps doesn't go pass 60 C when is overload.
I also did some research and it seems that a lot of people have the same issue with HWMonitor.
Just curious, what version of HWMonitor are you running?
The newest version. I check for updates and it says that I have the latest version.