I just looked at the forecast and you have nothing to worry about. General rule of thumb, if it's not getting above freezing or much above freezing for an entire day, there is a greater possibility that something exposed may freeze up.
For comparison, I never winterized our TC in the Seattle foothills this winter, avg about 5-8 deg colder than sea level. Parked in an un-heated (most of the time) shop. I did turn on a little electric heater a couple times when the temps got down to teens/20s. Water bottle in the corner of the shop on the floor never had ice
Camped a couple weekends ago in the mtns. It snowed. Fresh load of ice cold well water in the tank. Heat was off all night while we slept. No problems, none expected.
If you need confirmation that there won't be issues, tonight is the coldest night forecast. Put a little cup of water or a mostly empty plastic water bottle outside where it sees no sun and see how much ice is in it in the morning. Likely none and it certainly won't be frozen solid.
