Of course, it depends on how cold and windy it gets. In my experience, with the thermostat at 70-72, the furnace will keep the underbelly 10-12 degrees (F) above the outside temp. So you'll probably be ok down to about 20 (F). Below freezing, you'll either have to pump water from your fresh tank, or use a heated hose. You may want to put insulation on your low point drains and fresh tank drain. There's water above the valves that's exposed to outside temps. If it freezes, the ice can wick up into the tee and block the water lines.
If you have a refrigerator with ice maker or water dispenser, located in a slideout, the water feed line likely goes under the slide and is exposed to outside temps. It's a thin poly line that will freeze and crack at just below freezing. If you have that, you need to turn the feed line cutoff valve to OFF and evacuate the water from that line.
Keep in mind that weather reports often give you the temperature at a local airport or some other spot that can be quite different from where you're camping. If the weather forecast is for 20, where you are located it could be 25, or 15. The park where you stay can probably provide guidance.