This is one of the "advantages" of living in the Great White North. If you're travelling from the south to the north, where temperatures fall below freezing, winterizing is a must and conversely, de-winterizing when you're heading back down south. Some trailers come equipped with heating pads on the grey, black and freshwater tanks and that will certainly help when temps aren't too cold. Outside water lines can be wrapped with heated electrical wrap to keep them freezing overnight. Also make sure that heat is getting to areas that contain the water pump, lines etc. That being said, the only safe bet is to winterize.
We are heading off to the Florida Keys in the next couple of days, and as the trailer is currently winterized and we won't be in moderate, i.e. above freezing temps, for at least 1,200 kilometers, we'll be opting for a motel for at least the first night. Sucks, but that is reality.
Hope this helps.