Eh, not very much of one atleast when I grew up there. You get a few nice-ish weeks from late August-mid September with highs in the 60s and 70s and cool low temps with some rainy and cloudy days. But the fall colors don't start showing up til the end of September, but by then the weather sucks pretty bad, of course there are sunny days but it's too cold.
NW autumns are wayyyy better, especially in the willamette valley. When I lived in Corvallis for college, September and October were my favorite months. It's still pretty nice here in Sunriver, but the willamette valley easily has the best autumn.