A1 camper seems to have the ideal scenario ...
the quickest thing to freeze are the waterlines, as they are small and unprotected .. vs. the large 20 gallon or so jug which is ... well im sure you get it ...
being a bit of adventurer ... my buddies and i went out on a last of April first of May trout fishing trip in Algonquin park .. and sure enough we froze over ...
So .. no water ... except if you can drain like rwarrin has done .. and keep lots of water on hand inside, where the heat and temps good.
Electrical site is required .. but if out in the bush .. bring an extra deep cycle .. to help with the furnace ..
We find that the Aframe really holds heat .. as they are so air tight ... so ... with propane heaters inside it could be a very big issue . radiant propane heaters have set off out C02/propane alarm .. they were thrown in the campground recycle bin
if the worst case scenario persists ...use a Buddy heater but definately leave a window ajar.
enjoy .. late spring and early winter camping really is the best ..
2008 Nissan Frontier 4x4
2011 Rockwood A122