Moisture under mattress solutions please

I lift up the mattress, hold it up with a foot stool and let my fan dry out the area under the mattress. In cold, damp weather I might need to do that every couple of weeks or so. In hot, dry conditions I can skip it entirely. Regardless of conditions I check for dampness under the mattress every few weeks.

The area under my mattress was raw plywood. I greatly decreased the condensation problem when I applied several coats of paint.