This soggy weather keeps up, Seattle could pass the 'other' Washington in average rainfall
SEATTLE -- The locals know the drill: Seattle has the rainy reputation, but when you compare us to other cities in the "annual rainfall" tables, you'll find Seattle at around 37" a year is down in the middle of the rankings, behind less notoriously soggy spots like Miami, Houston, New York and Washington, DC.
Well, *maybe* Washington, D.C.
Turns out in the past few years, our incessant drizzles that run up the score on number of cloudy days and days with measurable rain have also been doing better in adding up in actual rain gauge measurements. The result is a number of recent years that have gone far past our annual average of 37.49 inches. The past three years, and four of the past five, have ranged from 44-48 inches.
The way NOAA calculates average rainfall totals is to take the past 30 years of data and update it each decade. Presently, our averages include the span from 1981-2010. But with a wet decade under way, I took a sneak peek of where Seattle is trending for the next update after 2020 is complete. From 1991 through 2016, our average rainfall jumps to 39.42 inches -- an increase of 1.93", which is quite a bit for a 30-year average (well, technically 26-year average at the moment.)
And that's not counting 2017, which is off to a very wet start with our record February in the making.
It edges us closer to some of the big cities that are ahead of us: New York City is at 42.46" and Boston is at 43.12 inches. That's... still a ways to go, but there is one major city that sees Seattle coming up fast in their rear view mirror: Washington, D.C.
Reagan National Airport's 1981-2010 average is 39.71", but doing the same math to update for recent years shows they're running a little wetter too: up to 40.46 inches. Still, that's within our reach, especially if 2017 keeps up and we don't go into a drought toward the end of the decade. Dulles Airport is a bit farther ahead at 41.51" but Reagan's closer to the city center.
Why have we been so wet?
It's been a bit wetter than normal because we've been a bit warmer than normal of late. Warmer air can hold more moisture, and, especially in our fall and winters, it's led to some rather wet months. We've set all-time wettest month records for March (2014), September (2013) and October (2016) this decade, and we're on our way to adding February to the list this year. December of 2015 is in 2nd place, October 2014 and 2012 are in 6th and 7th place, August 2014 is in 4th place, and April 2013 is in second place.
Long range forecasts just issued last week suggest a wet spring for the Northwest so we'll see if we can keep up the pressure on the "other" Washington.