re: Turtle's post -- I don't drink out of my freshwater tank but many people regret putting antifreeze in there. It is very hard to remove all traces in the spring. See: the top 2 threads in the winterizing subforum
Bryan Leipper has measured inside temps in cold weather and posted in the past about very moderate internal temp swings inside the trailer -- for California. One example here.
I can't imagine you have any worries in Tempe! I say this from a background of growing up in southern Texas and two days of 'blue northers' freezing down for two days at a time. None of this applies if you move your Airstream to even mildly higher elevations!!