Processor temperature goes up and down without explanation

i7-6700, other specs are irrelevant. Problem is this: AIDA64 and HWiNFO shows that my CPU temp is around 62-64C, idle. But, when I open my task manager and look at temp again, its around 35C. I’m asking HOW, WHY??! I close task manager, and the cpu temp goes back up to 62-64C, it doesn’t make any sense?