I'm having the same problem. While it's been rather humid/wet/rainy lately, indoors it says its a comfy 50% all the time.
We made a custom lid for the snake's home to put on a glass tank to keep the humidity in (as most seem to have problems with that in glass) but my humidity is in the 80s and 90s. :/ I don't have a snake in it yet, I'm just trying to set it up first. The lid is FULL of holes! But alas, 80-99 is way too high v_v it goes down to 60-70 if I keep one side of the lid open, so I'm thinking I'll put a mesh/screen on the back lid section for more air.... unless there is a better option.