I had some a couple years ago.  Emptied one bin in the winter and the corn stuck to the ring was still frozen.  Next bin had corn in it until summer/fall and had that nifty layer of rotten crap stuck to the walls probably 6-10ft up.  That's where the corn was at when we got down to 6*F overnight wile drying.  We have since decided to say the heck with it and shut the dryer down when it gets too cold.  Don't want to mess with that again.