We winter camped for many years with trailers that had exposed tanks. The main thing to look out for is your city water connection and outdoor shower if you have one. When outdoor showers became a standard on campers it became something I had to add bypass valves on the inside of the trailer. You need to disconnect city water at night and insulate your outside shower if you have one.
The black and grey tanks will not freeze in a few hours or even in a day. I never had any issues with waste tanks.
No man has a good enough memory to be a successful liar. Abraham Lincoln
2016 36FBTS Pinnacle
2016 F350, 6.7, 4x4, DRW, long bed
B & W Companion 5th wheel Hitch