Well... As someone else said in another thread the rule is "If temps drop below freezing you need to do something"
So, if you take a map of the United States. Draw a line about 1/2 the way up Texas, across the country, and all above the line, Winterize
Last Jan and Feb I went from Detroit (Above freezing) to Las Vegas (Above Freezing) to Arziona (Quartzsite, above freezing) to Las Vegas again (My daughter lives here, I"m in Vegas now) to Utah (Froze something) to Page AZ (cold enough to freeze) to Flagstaff to I-40 east to wherever I branched off to get back to Indy, Jackson, MI. and finally Detroit. I froze hoses (outside) along I-40 a couple of nights.
In all this weather the MH was ok because it was heated and all my plumbing is heated (some better than others less I take additional measures but at 20 degrees, no additional measures needed)
So, I-40 is in the freeze zone, I-10,,, Well, it idi not freeze where I parked on I-10 however last night in chat in another forum one of the SYSOPS who lives in New Orleans was telling me they have freeze warnings out, It freezes in the state who's name means "Sea of Flowers" (At least at Disney World)
So, I'd say if you are in the US. or Canada, Winterize. Mexico, optional