Around Oregon and the rest of the northwest the seasonal changes are definitely beginning to happen. In addition to the leaf change the rain increases and there definitely is about a 5-10 percent increase in the interior relative humidity. This change may seem minimal, but is just sufficient to begin to make the wooden structures within a home swell just enough to start making more noise by the increased friction. One case in point is my staircase leading upstairs to my bedroom where the treads have begun to squeak with walking against the skirtboards on the staircase into which they are mortised.
Now I realize that the noise drives some people absolutely crazy from squeaky floors. In most cases the noise from the floor originates because the subfloor and joist structures are coming loose from one another. There are a few approaches to fix this problem: shimming the subfloor from below or using some sort of screw to secure the subfloor to the joist. When you screw down the subfloor, you can toenail screw the subfloor to the joist from below. This proves relatively effective, but may often be difficult to do because of HVAC ductwork and wiring in the way. The other method I like is to use #10 trimhead screws because they have a screwhead diameter no bigger than 3/16″. The decking screws used for composite decking are best because they have threads running clockwise and counterclockwise that prevent the screw from backing out and really seating into the subfloor. If you can locate the joists you can screw down the subfloor from above. The hole is very minimal, and almost always the squeak will go away as long as you have contacted the joist.