Probably condensation or you have a small leak in some seals. Not a biggie, almost all Jeeps leak to some extent, you just have to keep up on it. Pull the carpets and floor mats (if you have any) up once in a while and let it air out. That is why some people pull out the carpets and put bed liner everywhere.
Actually a better place to post questions loke this is here: http://www.wranglerforum.com/f5/
I think you'll get more responses by people with your model Jeep.