Spokane’s ‘water year’ was 17th driest on record as new annual count begins

Spokane’s water year was the 17th driest since record-keeping began 140 years ago.

Greg Koch, meteorologist with the National Weather Service in Spokane, said 12.06 inches fell between Oct. 1, 2020, and Thursday.

He said Thursday’s two-tenths of an inch of rain at the Spokane International Airport pushed the city’s water year mark above 12 inches. Koch said about one-third of an inch fell at Felts Field, and some volunteer observers measured even more .

The 12.06 inches of precipitation that fell was 4.39 inches below Spokane’s 30-year average of 16.45 inches. That’s a 27% decrease.

“That is a significant shortfall for a place that receives only 16.5 inches per year,” Koch said.

He said the most significant precipitation deficit occurred late last winter and through the summer. He said Spokane was on track to have a pretty average precipitation year starting last fall and winter, but February, March and April – months when the area typically receives significant precipitation – were very dry.

“It was a very ill-timed shortfall for us to get into a pattern of dryness because so much of our agriculture and water supply is determined late in the winter and early in the spring,” Koch said. “The lack of precipitation that we got in the spring was very detrimental to dryland crops that were planted in the spring.”

As of Thursday, Spokane was still in the U.S. Drought Monitor’s most extreme category of “exceptional drought.”

Koch said Spokane’s driest water year was 1928-29, when 8.8 inches fell. The driest year before this was 2000-01 with 9.67 inches – the second-driest year since 1881. The 2014-15 year ranked 18th at 12.45 inches.

Koch said the water year runs October through September because the region receives the vast majority of its precipitation from October to April, providing a more accurate picture of the wet season than the calendar year.

As for the winter outlook, Koch said there is an above-average chance for a wetter-than-normal winter and a good chance of below-average temperatures. He said it’s unclear whether the predicted above-average precipitation will offset the deficit of the recent drought .