humidity and my js

So, I keep my js in the basement and recently, it's been very humid but the basement temp hasn't gone over probably 75 degrees. I noticed that my frets (especially around the first few) are fretting out quite a bit. I looked at the neck and it seemed very straight, so over the last 2 days I've adjusted the truss rod about 1/2 turn total. Is it normal for humidity to make the neck bow up like that? And will keeping it in it's case keep it from doing it again? In the 14 years of playing, I've never run into that problem before. Thanks.