Random Thought:Twilight, Vampires and Cold Air

I was watching a Twilight movie the other night courtesy of Showtime On-Demand and had a random thought pop in my head during the show.


If vampires are cold-blooded, does that mean that on  a cold day, no one can see their breath?

I mean, assuming they breathe, does that mean that their breath doesn't condensate when it reaches the cold air when they exhale? But if they don't breathe, that means that no one can see their breath on a cold day because there is no "breath" in the first place.

I bet the "cold air test" would be a good way to detect if someone is a vampire.