Four season, artic, extreme & polar (even 1/2 towable) are simply sales gimmick names to sell RVs.
All those packages mean that the underbelly is enclosed with either Darco (black fabric) or Coroplast (plastic cardboard) with a layer of Reflectix (shiny bubble wrap) above those with a 2", possibly 3", furnace duct blowing into the underbelly which in extreme, polar or artic conditions you'll most likely have frozen pipes, especially if not running the furnace.
If you'll be stationary for winter the best option his to rent a large LP tank from the local distributor with a contract to keep it filled, as you mentioned the furnace is a huge LP big.
If not necessary to be in those areas head south til you run out of those possible temps.
Danny & Linda
Sold my '13 Redwood 36FB
Currently rv & truckless