I live in CT and I'm using a Car Capsule. This is my first year using it so I can't speak from personal experience yet but they claim that because the air is being changed 3-4 times per hour the temperature remains more consistent thereby eliminating condensation. My car has only been in about a month and a half but so far so good. The air is filtered as well so no dust.
http://carcapsule.com/how-it-works/