Unless the trails are treacherously muddy or the rain is coming down in torrents, one can hike year-round in the Pacific Northwest (freshly fallen snow is merely an excuse to snowshoe). Our latest excursion was to Hamilton Mountain, another Gorge-hike, on the Washington side. While we can't seem to escape hiking on that side of of the river without getting a ticket (for example: the pass was printed at the wrong time, the pass didn't have the license plate number on it), this particular hike was worth the lame cost of the incorrect ticket.
I'm assuming Hamilton Mountain would be gorgeous year round, but hiking in the Fall meant that at times we were above the low cloud line and this fog made it feel as if we were looking out an airplane window. The fog misted in and out, occasionally interrupted by sun, revealing expansive Columbia sight-lines. And when the fog was denser, it lent a relaxed, ethereal air to the entire hike: 3.5 miles up followed by a relaxing descent.