I'm in northern Oklahoma where temps yesterday morning was 7 below. We have had one night at 26 below a couple of years back. These are actual temps and not a wind chill.
I run the blue stuff in all the water lines and traps. I also open the grey and black tanks however I do cover the dumps with wire mesh to keep the critters out.
I also remove all products/foods that can freeze and burst. I also pull the batteries and place them on a charger in my heated garage for the winter. Never left any kind of heater going in any of the campers we've had. There simply was no reason for heat.