This question comes up a lot - and those without a lot of experience with occasional freezes that are followed by a daytime above freezing may not realize that this is not an issue that requires "winterization."
First, your RV is a big lump of metal, plastic and wood. it does not freeze in a few hours. So, overnight lows as low as the low 20's just don't have enough time to make the underside and surfaces around the RV get chilled down to freezing.
Especially if you are living in the RV at the time. Running a heater at night, running water and all the systems during the evening as the day begins to cool down. Pretty soon the Sun comes up and things immediately start to warm up outside and this puts a halt to any freezing in your RV, too.
Now, for those that live where winter is more a less an extended period of below or near freezing that goes on for days, weeks and months this is different. Even if you are living in the RV (hope not) there's plenty of time for things to get very cold and yes, freeze.
Living in South Texas I've seen 100 degrees in February, but I've also seen last year's week long deep freeze with snow, power outages and ice. But we don't winterize... ever. And, we get by just fine, even with the RV in outdoor storage and not being heated or used.
Two years ago I went to Durango, CO in May. I parked my RV in the National Forest at 8,300 ft elevation. It froze every night, but was high 30's to low 40's every day. We even woke up to 3" of snow one morning. There were no pipes freezing and no winterizing needed. Of course, we ran the heater every night in the coach. Usually set at around 63 degrees. We don't want the dog to freeze.
2017 Winnebago Adventurer 37F
2016 Lincoln MKX Toad