My Thermometer is under my Kitchen Towel, Under the hide, the heat mat is under the tank heating the hot spot (in the hide). The thermometer is keeping an eye on the hot spot making sure i am able to see how hot it is. Never about 89 when the snakes not there, When my snake sits on it, it raises. 1 degree or so, but its bound too... Its like, having the probe in room temp in the air, then covering it with your hands for 20minutes, it going to raise.