We're in a similar situation in Indianapolis. Normally if it only gets down to 28 or so I don't worry about it. I drain the tanks and relieve the pressure in the water lines but don't blow them out. Friday night its supposed to get to 25, I'm going to run our small spaceheater and keep the inside compartments open that contain the water heater, pump, and under the sinks. It will be well above freezing where it counts.
2013 Roo 183
2012: 1042 Miles, 13 Nights camped
2013: 2772 Miles, 27 Nights camped
2014: 2259 Miles, 30 Nights camped
2015: 1644 Miles, 20 Nights camped
2016: 550 Miles, 11 Nights camped