Yes, and I recommend it in sub-freezing weather. It will keep your water pipes from freezing, within limits. I've done it and was successful in weather in the teens, but would not rely on it for much lower temps.
“Never argue with stupid people, they will drag you down to their level and then beat you with experience.” ― Mark Twain
'08 34' Classic SO, '12 Ram 2500 4X4, 6.7L Cummins.