Cover about 3/4 of the screen with foil tape or a damp cloth. Also having a large bowl of water closer to the heat source will help.

In my 40gal tank I have a hard time keeping it over 45. I added moss to the hides and will mist that every few days and during a shed I will keep it damp. This creates a micro climate of high humidity within the hide, and since it is also where your bp will be most of the time they benefit greatly from it.

How or what are you using to read your humidity?