Looks like HWMonitor is having fun pulling numbers from elsewhere.
Both Coretemp and Open Hardware Monitor are display a CPU core temp of 20C. Core Temp usually nabs its readings from the on-die CPU Core sensors, which are most accurate at load.
If I had to place bets, it would probably be both of those. To double check (triple check, rather) I would download AMD Overdrive, and observe what numbers it gives you for the core temps. If they match up, you're good to go.