October breaks monthly, daily rainfall records in Spokane

As Halloween brought October to a close, meteorologists say Spokane has never received so much rain in any single month.

Through early afternoon Monday, 6.22 inches of rain fell on Spokane, shattering the previous record for any month – 5.85 inches set in November 1897, said Jon Fox, a forecaster for the National Weather Service in Spokane. The third-highest amount is 5.71 inches in May 1948. Records have been kept since 1881.

The city saw 0.91 inches of rain on Sunday alone, which set a daily record. The previous record for Oct. 30 – 0.70 inches – was set in 1990.

But the rain kept falling after midnight on Sunday, bringing another 0.36 inches for a two-day total of 1.27 inches at Spokane International Airport, the city’s official weather reporting site.

“It rained and it rained and it never stopped,” Fox said.

The October total is more than a third of what the city normally gets in a full year, which is 16.53 inches of annual precipitation.

This October’s rain total is more than 5 inches above normal.

And only five days this month were rain-free.

The heaviest rainfall on Sunday night and Monday morning was confined to the Spokane region and areas to the northeast and into North Idaho.

One location at Mount Spokane reported 1.5 inches of rain from the overnight storm.

The heavy rain was triggered by a combination of two low-pressure systems along the Pacific Coast – one offshore of Washington and another off California.

Together, they created conditions for upward motion, or convection, in the atmosphere, which allowed for the heavier rain accumulations, forecasters said.

Rain clouds extending from nearby mountains may also have enhanced the storm, forecasters said.

Spokane is one of 21 locations across the Inland Northwest to set October rainfall records.

Topping the list was Priest River with 9.26 inches through Monday morning, followed by St. Maries at 9.19 inches and Boundary Dam at 8.76 inches.

Boundary Dam has more than doubled its previous monthly record of 3.97 inches set in 1968. However, the dam’s weather records date only to 1965.

Elsewhere, Kellogg had more than 8.8 inches; Colville, 5.82 inches; and Rosalia, 5.9 inches.

Pullman, Moscow and Davenport all had record amounts of around 5 inches for the month.

Of the ten highest monthly precipitation amounts, there are only four months not on the list: March, April, July and August.

A little more rain Monday afternoon wouldn’t come as a surprise, Fox said.

“I wouldn’t rule out some showers tonight during trick-or-treating, but it won’t be like last night or early this morning,” he said. “It’ll be pretty hit or miss.”

In addition to showery weather, the departing shot of the Sunday night storm should bring windy conditions with gusts to 36 mph this afternoon. Steady southwest winds will range from 14 to 20 mph through this evening.

The weather service posted a hazardous weather outlook for Monday because of the winds, which might gust to 40 mph in some locations of the region, including the West Plains in Spokane County and the Palouse.

Reporter Chad Sokol contributed to this report.