Could it be
Here you go. I also couldn't believe it. Maybe the sensor is faulty? I live in Russia and the temperature is 0C outside. Room temperature is around 26ish. Also, I edited my post to make things more understandable. I was at around 10C when only Armbian was installed (no heatsink). Then once PiHole was up, I hit around 20C (still no heatsink installed). Then I installed the heatsink and went down to around 13C from 20C. As I previously stated, mine is indoors.