If you go to a campground with electric hookups take a small electric heater. Set it on a safe place, such as, on the stove. We have one of the little cube ceramic heaters and it does a fine job of keeping us warm. When boondocking I set the furnace thermostat at 55 and throw on a couple extra blankets at night. Also, crack a window and a roof vent to reduce condensation from building up inside.
When boondocking never let the battery go below 12.0 volts, or 50% charge, to help prevent reducing battery life.
My Great Wife Joyce
2018 Jayco Jay Flight 21QB
Formerly owned 1705T and 2310H
2012 F150 4X4 SuperCrew EcoBoost w/Leer Cap
Reese WD Strait-Line Hitch
Amateur Radio K3EXU