RVing in the winter

If you are going to be using the rig and keeping the heat on, upper 20's is usually not an issue. (If you have exposed black/gray pipes, you might drain before a cold night but no much else to worry about).

You still want to plan for colder weather. While it may be unusual, we got caught out in -5F in southern New Mexico one year for 4 days straight when the average was supposed to be what you are looking at. We were going thru a 30lb tank of propane per day just to keep the rig in the mid 50's and the RV park stopped selling to people not staying in the park because they were worried about running out.

In my limited experience with several motorhomes, upper 20F temps overnight hasn't been a show stopper, as long as things warm up during the day. So, you could probably not winterize under the situations you describe. If there was a more extended period of sub freezing temps for more than a day or two, without a daytime thaw, I would probably start winterizing, but it's a personal decision.
Or, try to seek warmer climes.