I'm just south of you. We have waited to winterize until mid-December for the last two years - the longest the temperature has gone below 30 before mid-December has, lately, been about 8 hours. We have had no problems.
We have also camped in this area without problems in December and January with two exceptions: a freak snow storm in October which froze our almost empty fresh tank for a couple of hours and camping in January with 20 degree overnights where our fresh water hook up hose froze overnight. The pipes in the tt were fine - one tt with heated insulated underbelly and one without.
