When I lived in Seattle I almost never rode in the rain, which of course is from September to May. And really, I just didn't.
I went back a few years ago, taking my bike with me on a cycling vacation in my old town. Just did some rides around, met up with a guy from here on the forums too. The first thing I did when I got to Seattle was made a trip to the REI store (which was new to me, the old store on Capital Hill was long gone I guess) and bought myself a Showers Pass jacket. I took it with me everywhere, and needed it. Since it was May, the rainy season hadn't ended yet, and I was there to ride. I rode in the rain every day of that trip. Twice I ended up in big downpours, actually unusual for Seattle, once out at Marymoor, and once coming back from Ballard. I rode back from Marymoor in the rain as I had no choice, but I ducked in Puget co-op and had some food and waited out the second one. That jacket came in really handy.
So since I've been back in NYC, I have yet to use that jacket in 5 years. My wife uses it for running, but I just avoid the rain.
Great jacket though, highly recommend it.