It varies a lot depending on where you are. Phoenix is normally a little warmer during the Winter than the rest of the state. It did freeze this year several times in parts of the valley. We spent some time in Catalina State park down by Tucson during Dec. Jan. last year and had temps of 21-22 at night with snow and wind. Up to the 50's during the day with wind. Froze the water hose every night if not brought in. In White mtns or along the Rim it's very cold with lot's of snow. Most camp grounds are closed.
Dave