It pisses down there at least 300 days of the year. Just as it does generally speaking in the entire area of the Pacific North West - Canadian or otherwise.Not too relevant to the original question, but... Just so no one gets the wrong idea, that is mostly only the coastal area. Much of the PNW is very dry including eastern Washington, eastern Oregon, Idaho and Montana (all part of the PNW by many definitions). In fact you often don't get far from the coast before the climate changes drastically. Over the Coastal Range and it gets pretty dry, over the Cascades and it gets very dry. A major portion of the PNW can accurately be called desert.
On the TA, being unfamiliar with the area, I kind of expected wet Oregon weather for a while and the first day we headed inland we were very quickly in dry climate and it remained that way until we were out of the PNW.