How cold does it have to be to winterize the RV?

Usually takes extended periods of hard freezing for pipes to freeze, so if you're getting into the high 40's or above during the day you're *probably* ok. To be safe, you could drain the water heater and open low point drains. I would probably just run heat on lowest setting and open cabinet doors. This assumes you have no exposed water lines. Just my $.02. Have a great trip.