.... And as a side to allthumbs, who by the way is righteous ....
I live in South Central Kentucky where it's humidity he!!. Most of the time my boxes are out of the case and in the open. I have yet to have a problem. Temperatures fluctuate wildly and regularly and humidity during the warmer months is just plain stupid. My sinuses have more problems than my guitars.
A good guitar is built for extremes. On the other hand, a spring rain can make mush out of a $2000.00 axe.
les