When cold weather is approaching it's a good idea to turn the heat pads on at least a day in advance, also wind is a lot worse than frost alone.
Your water lines should be fine down to a certain temperature as long as you have your propane furnace running and make sure no warm air can escape from the underbelly, anything exposed will freeze right away though.
Every RV(er) is different.
2018 RAM 5500 Laramie CC
Riverstone Legacy 38RE, 960 Watt Solar, 6x6 Volt AGM Battery Bank, Freedom SW 3012 Inv/Charger