most of the winter is in the 20s, and closely followed by the teens, really. sometimes we get colder periods where its (more rarely) in the single digits, but those dont last too long usually, maybe a week or two.. and then most of the later season (later march/april) is around 30. its rare that it goes below zero, but it seems like we always get at least a few days where its cold as fuck. it was -30 at night for three days last year. killed my car.. it hated it. oh, and we also get the total opposite. no joke, it was 60 degrees in january one day this year. we were riding 50+ degree spring/summer slush one day. it was weird. that was after the -30 period. then it went back to the usual 20s. the PNW is known for its inconsistent weather.
i definitely wouldnt live in your CAR, but a camper with REAL heating would be totally fine and pleasant.
the ultimate way to bum it would be to have your camper AND your car. park the camper somewhere and leave it while you stay in it, but move it around every couple days so people dont get weird about it, and then have your car to go around town when you need food or whatever. unless camper means a camper on a pickup, in which case you can treat it as a normal car.
it would just be lame to park the camper up in the EC parking lot and have to stick around there all day every day (if thats what you were thinking... people have done it before). keep in mind EC has NO apres ski type stuff or stores, at all. its a ski area, period... which is nice, because people actually go there to ski/ride. but youll have to go to stores for food. the douglas breeze in is about 11 miles from the EC parking lot and has all your basic foods to live off, or theres A&P across the bridge which is just an additional mile, and theyre an actual grocery store, so itll save you some money.