Shoot!!...gettin COLD tomorrow night!...got to winterize!

I wouldnt give that temp for one night a second thought. If you are really concerned you could just turn on the furnace at the lowest setting on the thermostat. My guess it it would only turn on a couple times. Just not worth having to clean all the antifreeze out of the lines for one cool night. I have reservations through the end of october and have no intensions of winterizing until then. If need be I will run the furnace at night like described above. I had to do it this spring and I will do it in the fall. Heck we even got snowed on this spring on our first time out.