This is only half true... At moderate cold temps just bellow freezing humidity does accelerate the risk of frostbite a lot and is a huge concern, but as the temperature continues to fall and is well bellow freezing humidity plays less and less of a factor, while exposure and drafts play a...
As for your question on mice jumping they can jump about 12" vertical, I have seen them many a time nearly jump straight up out of a 5 gallon bucket... Give them anything to grap with a little grip like a wood wall and they can pretty much shoot right up said vertical surface....
Also with any...