A funny thought about vampire physiology

Vampires don't generate their own body heat, right? They're cold-blooded. They cool or warm to the ambient temperature. Clothes would insulate them somewhat, but ultimately could only slow down the process.

So ... if a vampire is outdoors for too long in sub-freezing temperatures, wouldn't they freeze solid?

::pictures the Fanged Four taking shelter in an unheated cellar, and spending the rest of the winter as statues::