In the scene where Mr. Freeze is in his hideout, singing "White Christmas" along with his goons, it is obivously very cold. And yet, you can't see anyone's breath when they speak, what's up with that?
Also, you notice that although the men are apparently FREEZING, there's one woman wearing hardly anything, just some skimpy outfit, and yet she doesn't seem to be cold at all!
If you look at the guys, they might be cold because A: there is enough humidity in the air so it wont show, or B: it might be the fact they are sitting on ice blocks.