RVing in North during Winter months.
I'm not sure how far north you are thinking of coming but as I look out the window today it is -30 with a windchill driving the temp to -40 (celcius)......... that is tooooooooooooooooooooo cold for camping in Manitoba (or North Dakota which is south of me).....the campgrounds and parks all closed by Thanksgiving (Canadian version in October)..... I have a Triple E Class C with heated tanks, insulation, a furnace, 1500 watt ceramic heater and heat strip in the A/C unit and it is comfortable to about -10 Celcius....possible to about -20 celcius but beyond that I wouln't even try.
Hope that helps...
Tim Brown
(looking forward (desperately) to spring)