We live just north of I-90 (Idaho,) take that route fairly often through Washington and Montana, and would probably winterize. This means no on-board fresh water, but you can do a manual toilet flush with a water jug & some antifreeze, or put water down your sink, w/ same. (Windshield washer fluid qualifies as antifreeze.) With a winterized AS, we take a lot of water bottles.
You might be absolutely fine most of the time without this precaution, but you do have some serious mountain passes to go over on your northern route (like Lookout Pass in Idaho,) and even in New Mexico. Winter comes early to the high country.
If you are stationary for a while in Portland it's quick and easy enough to get your water back and functioning again. We're not do-it-yourselfers, so we tend to get the winterizing done at an RV service center, but if you have your own means of blowing out the pipes, you can probably winterize on a more ad hoc basis.
We did drive once with the furnace on during a cold snap (April in Utah) but prefer not to.
You could easily encounter a snowstorm in the mountains in Nov.-Dec. Even with beefy snow tires, it's best to wait it out somewhere safe. Some stretches of highway are not plowed as promptly as one would like.
Had you thought of taking I-80 to I-84 on your way west? You do have to cross the mountains of Colorado, but I-84 is a much lower route in elevation, with fewer passes to contend with.
I've noticed that we tend to be more cautious than most folks on this forum, however.
Linear Mode
