Realistically, they are all three season i.e. down to 32 degrees. Up here in Montana, the dealers even with the enclosed heated underbelly's won't promise all year camping. They call them 3.5 season units. So, instead of 32 degrees, you get maybe 20-25 degrees and the "western" packages and "polar" come with two big propane tanks so you can burn it like it's free as noted above. And I am not towing a trailer when there is a foot of snow on the ground anyway as there was from Dec to start of March here. They really ought to sell those units for Tennessee imho. I guess they could be four season there. It is nice to know its on there, but not essential to me.
