I'll pass along some advice on humidity and solid wood instruments that I got awhile back. I've had a solid spruce top/mahogany back and sides Martin D15 custom guitar for 4 years, and so far no obvious humidity problems that I can tell. I live Illinois where we go from 90+ degree F summers and 70%+ humidity to negative temperatures in the winter with extremely low humidity outside.
When you move your instrument from one climate to another (indoors to outdoors, outdoors to indoors, etc) always keep it in a hard case. Let the instrument adjust to the climate in the case for an hour or two before opening it. This lets the instrument slowly adapt to the humidity/temperature level with the case acting to prevent extreme swings in climate - the humidity will slowly creep into the case, acclimating the instrument to it's environment.
You just really want to avoid going from extremes. Let the instrument adapt.
I've heard laminates are way better than solid woods as far as getting damaged by humidity, and i have a laminate top/side guitar that i've literally taken all over and not cared much about babying it. It's an Alvarez RD8, was my first acoustic, and is my "take anywhere" guitar. It shows no obvious signs of distress despite going from inside to outside and cracked open immediately outside in the summer, spring, and fall. it's also flown in the cargo hold of an airplane and had no issues as a result.