When Charlie and Alex first enter the frozen hospital, the character directly left of Charlie, supposedly dead and frozen solid, blinks.
Charlie gives his Zippo lighter to his son at the very beginning. After that, Charlie uses the lighter several times that he gave away earlier and his son isn't with him.
When Tim & Marley are waiting for help and talking by the fire, Marley has no gloves on. When they hear the sound of a helicopter and stand up, her gloves are on again.
Gary and Cole report that everything is an arctic wasteland with noting left, yet in the next shot, undamaged conifer trees are abundant.
After Charlie and Alex use the torch to thaw the frozen door and enter the hospital, they pass a frozen man and say "we're too late." In the next shot, just as the camera pan reveals the same frosty character, the frozen man blinks.
The land is frozen. However, you don't see any vapor when people breathe.