Expect A Soggy Halloween As The Northwest Breaks October Rain Records

Oct 28, 2016

A break in the showers for much of Friday won’t stop Seattle from busting through the all-time record for rainfall in October. Heavy rain all around the Northwest over the past couple of weeks had many locations already charting unprecedented levels, says knkx weather expert Cliff Mass.

And more wet is on the way.

Sea-Tac Will Chart Record Rain This Weekend 

“Seattle is very, very close to beating its all-time record, which is 8.96 inches. That was in 2003 —for Sea-Tac. And right now we’re about three-hundredths of an inch below that,” Mass said on Friday morning.

“And I can guarantee you that we’re going to hit that either later today or tomorrow.  So we will break the all-time October record at Sea-Tac.”

Records at that station go all the way back to 1945, making it more widely watched than Northeast Seattle, where they only span back to 1986 and the record was already beaten on Thursday. But Mass said it’s impressive to consider not just the Seattle stations, but many others all over the region.

He says in Olympia and Eastern Washington, all-time records for October rainfall have already been charted in seven or eight major locations.  

“So, there’s no drought in Eastern Washington now. Western Washington is wet. Western Oregon is wet. Even California – people aren’t talking about this,” Mass said, “but they’ve been hammered by precipitation from roughly San Francisco northward.”

The reason for all of this, Mass says, is a persistent trough of precipitation in the eastern Pacific that has been pushing the jet stream southward, across California and then towards us.

“That’s why they’ve been wet and we’ve been wet,” Mass said.

Drier Friday And Saturday Evening

“Today looks pretty decent,” he said of Friday. “There’s a few showers that are moving through right now, especially around the Olympics and North Cascades. But I expect generally dry skies for much of the afternoon, maybe even a little bit of sun, temperatures getting up to around 60,” Mass said.

That’s warmer than normal.

But then another weather system comes in from the south Saturday morning, bringing clouds and more rain that Mass says will spread through western Washington and the Cascades.

“So I’m afraid the rain comes back again and temperatures only getting up to around 55,” he said.  He predicts a break on Saturday night.

“So we’ll be dry Saturday night if you’re out there,” Mass said. But then another system comes in on Sunday.

“I expect Sunday to be even wetter – highs again around 55 and then, looking into next week, there’s system after system, none of them that strong, but there’ll be continued rain on and off through the rest of the week.”

Go Trick or Treating Early If You Can

Mass says staying dry on Halloween could be challenging. Have an umbrella handy if you can't get out early.

“It’s going to be dry in the afternoon right before, but right now the models show a system coming in that evening. So maybe an early trick-or-treat jaunt to people’s houses might work, but then it’s going to get wet.”

To hear the forecast and discussion of how global warming simulations suggest October’s record rain will occur more frequently in the future, you can click on the “play” icon at the top of this post. The weekly knkx feature 'Weather with Cliff Mass’ airs every Friday at 9 a.m. immediately following ‘BirdNote’, and twice on Friday afternoons during ‘All Things Considered’. The feature is hosted by knkx environment reporter Bellamy Pailthorp. Cliff Mass is a University of Washington professor of atmospheric sciences, a renowned Seattle weather prognosticator, and a popular weather blogger. You can also subscribe to a podcast of ‘Weather with Cliff Mass’ shows.