In South Alabama I would NOT store my fabric in the garage as I'm sure it would get moldy out there in our very humid climate. (One especially damp summer I noticed the inside of the cabinet doors were a bit moldy.) If you are in an area that the humidity stays really low, it may be okay. Small holes in plastic boxes where it can breathe is probably a good idea as long as bugs don't get in. My biggest concern, if I stored fabric in an out of the way place like that, is keeping it organized enough that I will use it and not just forget about it because it is too hard to find what I want for a project.