and for the requiem we have....
VtR page 174
Temperatures over 200°F+ might count as feeble fire (or at least set the panic of Rotschreck crawling into a character's mind).
Prolonged exposure to to freezing temperatures might force a character to expend a Vitae or two to avoid frostbite. In the most extreme case, a Kindred could freeze solid and immobile--not harmful in itself, but eventually the character starves into torpor if she doesn't burn from exposure to daylight.
for VtM and VtR...
okay...so they are not immune and can feel it when it happens...they can feel the air becoming colder...or hotter...