What does your enclosure look like, does it have a screen top? Wrap it in tinfoil if it does. You can add some sphagnum moss and wet it down too, but don't soak it.
You can also increase the size or your water dish and/or add an additional dish closer to the hotspot. Add water dish or humidity box inside the hide, allowing room for the snake of course, the animal should not be kept wet.
The most important time for humidity is around shed, you can spray the enclosure periodically around this time to temporarily increase humidity.
What is the temperature in the enclosure? it can also affect the humidity of your enclosure
Another thing to try in dryer months/locales is this... Buy a "loofah" sponge or two (available at Wal-Mart) and stuff the cylindrical holes that run the length of the sponge with sphagnum moss. Then saturate the sphagnum moss thoroughly with water, allowing excess water to drain off. Place the sponge(s) close to the hides inside your pet's enclosure. My snake is about ready for a shed, and I've boosted my cage humidity from 53 to 65% in a little over an hour.