I had not driven in Seattle for quite a long time and was there on a Wednesday before noon and shocked at how bad it was on 5 and in the City. Left Dodge many years ago. Domleave as early as you can especially if it is before Labor Day when people try and get out of town early for the weekend. The worst traffic is always near the Four Cities which includes Portland. Not sure where you are going in Vancouver, but when I visit my brothers in Portland I always take 205 before Vancouver.