It's do-able, but I personally don't think it'd be very enjoyable because it rains so often during those months. As B.Carefree mentioned, visibility is an issue. You are much more likely to be unnoticed by cars in wet, windy weather. If you were planning on it, I'd recommend hotels or warmshowers hosts over camping. The weather can be fantastic on the coast when it's not raining, but it rains ALOT during the winter months. Article

By Vancouver, I'm assuming you mean Vancouver BC? Were you planning using the ferry system to get to Washington?