Weather Blog

Seattle ends "water year" a bit behind

Seattle ends "water year" a bit behind
Happy first day of the official rainy season in Seattle. There's probably some irony that it's still sunny outside, but if you've seen the forecasts lately, you know this is likely the last day we'll be sunny and 70+ for a while -- possibly until next spring.

But October 1st is also the day we reset the annual rain gauge that measure the "water year."  In addition to tracking rain from Jan. 1 to Dec. 31, we also track rain between Oct. 1 and Sept. 30 since the bulk of our rain comes in the fall and winter.  That way, we can better gauge how a true rainy season shaped up, instead of cutting it in half and spreading it across two measurements' like the calendar year rainfall total does.

This year, Seattle's water year rain ended up at 34.05" -- about 3" below our normal of 37.07". Eight of the 12 months were below normal, with November, February, May and September well below normal. The only really relatively wet months were December and August.   This is somewhat surprising because La Nina winters historically tend to be wetter than normal -- although if you remember, the Cascades ended up with a higher snowpack than usual.

Here is the monthly breakdown:
Month Observed Dept. from normal:
October 3.32 +0.13
November 3.71 -2.19
December 9.08 +3.46
January 4.26 -0.87
1.47 -2.71
March 3.65 -0.10
April 1.90 -0.69
May 0.89 -0.89
June 1.64 +0.15
July 0.48 -0.31
August 2.87 +1.85
September 0.78 -0.85