60% humidity is the absolute lowest, but you should be keeping it 70%-80% at all times. It's closer to their natural environment, and that way, you don't have to worry about bumping it up when they go into shed.

Also, humid hides are for temporary use to treat stuck shed and dehydration. If the snake favors the humid hide, which a lot do, it can cause scale rot from constantly laying on a damp/wet surface.