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.
Mike. Comments are anecdotal or personal opinions, and worth what you paid for them.
2018 (2017 Sprinter Cab Chassis) Navion24V + 2016 Wrangler JKU (sold @ ????)
2016 Sunstar 26HE, V10, 3V, 6 Speed (sold @ 4600 miles)
2002 Roadtrek C190P (sold @ 315,000kms)