I think you need to invest in a thermostat.

A thermostat regulates the heat from your UTH while your thermometer just reads how hot the bottom of your tank is.

Most heat sources running wide open and unregulated by a thermostat get way too hot for a snake.

A lot of people use Helix, Herpstat, and Johnson thermostats. I have experience with Helix and Herpstat and they are both excellent products.