A final update on the question I asked back in the spring. It was -13C in Lethbridge and remained cool for quite a while once we were home, north of Edmonton. I kept the trailer plugged in in my driveway and eventually went and dumped water and sewage and there were no problems at all. It was a cold spring in Edmonton so I hope not to have to worry about this in future. Thanks for all your feedback.
Thanks everyone for your helpful comments. I am in St George, Utah and it was well into the 90's today....hard to believe I'm even asking the question! We are doing about 7 hours a day...Brigham City tomorrow, then over the Monida Pass to Dillon, MT, then Lethbridge, AB, then home to Edmonchuk My main worry is freezing up the pipes...so if the RV is warmed up once we stop, it sounds like I should be OK, but if in doubt I`ll open the low point drains as suggested.
I am heading north to Alberta after wintering in AZ. It looks like I will hit some -10C overnight temps. I'd rather not winterize the unit and I don't like the idea of towing with the heater on. Is the Polar Bear package enough insulation to prevent freezing of my waterlines etc.?