Cliff Mass, simply by moving the starting point further back to October, says it is really just the second wettest.
But, as a history person, I am going to pick on the use of the phrase "in Seattle History."
So, obviously, you know where I'm going. Record keeping on this sort of thing started in 1894. Obviously, even if you are going to only count the white dominated part of our regional history, there are at least 4 decades of rain seasons that aren't accounted for.
And if you're a broad minded progressive, you'll quickly point out that Seattle History did not start with the Denny Party landing on Alki, and that somewhere back in the history of all humans along Puget Sound (even in its most recent post ice age state) there were likely much wetter winters.
1894 though, right? Doesn't that make sense?
Let's go back five years. Washington was poised on the edge of a new era. After decades of federal servitude as a territory and economic servitude as a commercial outpost to San Francisco, Washington started the year with a constitutional convention with an aim at statehood. Then, it seems like every city in the state caught fire, most notable Seattle. It burned to the ground.
While on the face a long series of tragedies, the 1889 fires gave the cities an excuse to grow beyond their pioneer and territorial constructions and build something better. The year after the fire, Seattle was able to stretch beyond Puget Sound rival in population (42k to 36k) and never looked back since.
The fire laid waste the city, but it gave the people there the opportunity to build a brick and mortar, modern, and fireproof city. And, if you think of this new city as the historic Seattle we know today, then 1894 is as a good enough year as any (since it gave the city long enough to rebuild) to start recording historic rainfall.