I live in East TN not far from Pigeon Forge. The weather fluctuates from mild to cold with some chance of snow. With preparation you can full time in a 5th wheel without too much problem.
In March of 2011 I accepted a new job up in Northern Michigan and decided to take our motorhome to live in until we could find a decent place to rent. When I arrived in Ironwood there was still snow on the ground and the temps were dipping in the low teens, we got 2' of snow in April. Since I was going to be traveling quite a bit I didn't want to rely just on my propane furnace. This issue was compounded by the fact that I did not have full hookups and only 20 amp outlets to plug into. I monitored power consumption often to confirmed consumption.
Here is what I did to try and survive.
I ran one extension cord into the basement for power and hooked up my house power to the other.
I did not leave my water or sewer connected. I took advantage of the campground shower to limit water consumption in the coach.
I got a remote temp monitor for my basement so I could monitor the temps.
I ran a small cube heater in the basement, I used a thermostatic plug to control the on/off
Shop EasyHeat Roof Heat Cable Controller at Lowes.com
These can also be used on water line heat strips.
I sealed up any openings in my basement to prevent air infiltration.
I stuffed a pillow in my fantastic vent opening and sealed the Coolmatic fan as best I could.
I have dual pane windows which do a pretty good job and limiting cold infiltration. My front windshield was a huge problem. I did have some large sun screens that fit the front window, I put some blankets across the front, then the sun screens, and then closed the curtains. It did help with cold infiltration, the reflextix would probably be a good option where you can use them.
I slept under heavy blankest since the cube heater running in the LR wasn't large enough to heat the entire coach, the bedroom would be in the low 30's sometimes in the AM. Most days the temps in the coach were in the 50's, if it got too cold I'd run the furnace to take the chill off. I grew up in Northern Wisconsin so these conditions were familiar to me.