Class A diesel units are going to have some version of Aquahot diesel fired baseboard heat. This also heats the wet bays and keeps everything nice and toasty. If the unit you look at does not have this then pass. All the plumbing in inside the coach so even if it got really, really cold you could add a small electric heater or a light bulb or 2 to the wet bays and you will be fine. We have traveled in most every weather you can imagine and we have been fine. I must say that when the company sent us to ND in January (20 below zero) we passed and drove our car and stayed in a hotel!