Hey baffled, i'm not heard of the fill and drain that you mention, i really sympathise with you growing in the desert, it's gonna be really hard to keep temps down. There's only a couple of things i can suggest, run your lights at night when temps are lower and try getting a cool tube for your light. If you can keep the light cool you'll stop a build up of heat in the grow room. I've never had any probs with low humidity, i'm usually tryna lower it lol I'd just put more water in the grow room, i'm assuming you've got space to put down some bowls of water. You could also try spraying the room with water just after lights out. Good luck