Accurite makes a great thermometer that you can get at Wal-Mart for around 10 bucks. It will say indoor/outdoor. Put the probe on the warm side and the unit on the cool side. You will be able to monitor the temps on both sides with it. Look over with the a/c filters and stuff. You absolutely need a thermostat on the heat mat. They get extremely hot. IMO if I could get the ambient air temp up to around 86-88 I would probably unplug the heat mat for tonight. I would rather my snakes belly to be a little cool for one night than to wake up with a nasty burn.