How cold is cold? 25F at sunrise and most RVs are just fine running the furnace. Much below that you will need to start adding electric heaters to any exposed tanks and pipes. At some point pipes in the walls and floor may start to have freeze ups with additional measures needed or you can winterize and use bottled water. Your furnace could be running near continuous so an extra cylinder or two of propane may help along with an electric space heater. Also need to add heat to the outside fridge compartment to keep the system working.
