we had many(too many) occasions for temps in the -10 to -15* range at night. In fact, more than anyone could remember. Certainly weeks below freezing. Just to throw another question in this mix.........wind chill?

For example, our boat sits right on the edge of the great white north all winter. The storms come whipping in from there with cold temps and colder wind chills. If the temperature is in the negative teens and the wind chills are in the negative 20's and 30's, does that suck what little warmth there is out of the hull and insides and batteries or does it just freeze skin?