the temps you want to monitor are not the top of the tank, but the floor, right above the substrata. if you have the correct temp reading at the top, like you do, then your snake will be roasting. You want the temp on his warm side to be around 90, right above the substrata, about an inch or so above it. Think about it, your snakes height is about 2 or 3 inches high, even if it is a couple of feet long. The ground temps are the ones that affect the snake the most.

You also want to put a cool side hide in the tank as well. The cool side should be around 80, again, thats 80 a couple inches above ground height. There fore your temp gauges need to be near the bottom of the tank. You may also want to invest in a digital temp probe.