Records fall amid Puget Sound region’s first storm of the season

The first major storm of the season has arrived, and rainfall records have fallen over the past few days while thousands were left without power.

Puget Sound Energy
Seattle City Light
Snohomish County PUD
Tacoma Power

Season’s first mountain snow this weekend heralds the onset of fall

Rain moved into the Puget Sound region on Friday afternoon, breaking the Sept. 17 record for both Bellingham and Quillayute, which saw 1.45 and 3.05 inches inches respectively for the day. The previous record for Bellingham on that date was 0.93 inches; Quillayute record was 1.97.

On Saturday, showers increased, with another daily record falling in SeaTac, which saw 0.81 inches for the day. The previous rainfall record for Sept. 18 in SeaTac was 0.78 inches, set in 2010.

48hr rainfall–up to around 5" in the rain forests of the mountains, only about 0.4" in the lee of the Olympics between Port Townsend and Quilcene. Around an inch in the Seattle area. Portions of Eastern Washington did not see much at all (Wenatchee to Omak for example). pic.twitter.com/cinYSmBvei

— NWS Seattle (@NWSSeattle) September 19, 2021

While chances of thunderstorms were “slim” on Friday, KIRO 7 meteorologist Morgan Palmer had said there would be a “better shot” on Saturday or Sunday afternoon.

“National Blend of Models puts 30% chance of thunderstorms for Seattle area,” Palmer said.

At one point Saturday afternoon, the temperature fell from 62 degrees to 53 degrees at Sea-Tac Airport. The wind was gusting to 30 mph and a quarter inch of rain fell in 40 minutes.

Pictures of Lake Washington taken an hour apart ( 1:30 pm and 2:30 pm ) this afternoon. #wawx pic.twitter.com/iMMpfyCE3X

— NWS Seattle (@NWSSeattle) September 18, 2021

Sunday afternoon was also wet across the Puget Sound region as showers and thunderstorms moved through Snohomish and northern King County around 4:30 p.m.

Since Friday, Bellingham saw 107% of its normal rain for the entire month of September. Seattle saw 86% of its normal rain for September, Hoquiam at 85%, Olympia 77%, and Quillayute 73%.

Rain totals since Friday & percentage of the normal rain for entire month of Sept. Rainfall map as well.

Bellingham 2.16" ( Sept. normal 2.01" ) 107%
Seattle 1.39" ( 1.61" ) 86%
Hoquiam 2.16" ( 2.53" ) 85%
Olympia 1.57" ( 2.04" ) 77%
Quillayute 3.33" ( 4.56" ) 73% #wawx pic.twitter.com/IqiCID4mUW

— NWS Seattle (@NWSSeattle) September 20, 2021

Wind and rain also saw as many as 114,000 Puget Sound Energy customers go without power on Saturday, largely centered in the South King County area.

Over the last three months, Seattle has seen an estimated 0.13 inches of rainfall. If that number had held until Sept. 20, that would have represented the lowest total for the summer season since 1945.

In a typical September, Seattle typically sees an average of 1.61 inches combined across the entire month. Between Friday and Monday morning alone, Seattle was expected to get between 1.5 and 2 inches in just that 72-hour period. The city saw 1.39 inches, according to NWS Seattle.

The City of Seattle had warned that power outages in some neighborhoods “are unfortunately inevitable and inconvenient.” City Light advises that all residents check the batteries in flashlights, camping lanterns, and “other flame-free backup lighting options” to prepare. You can monitor outages at this link.

That is all part of what University of Washington climatologist Cliff Mass calls “the storm we have been waiting for,” following a summer of scorching heat, dry weather, and a record number of wildfires.

“This rain will mark the end of the wildfire season in the Northwest, the remaining fires will rapidly decline with the massive moisture, high relative humidity, and MUCH lower temperatures, with highs dropping into the lower 60s,” Mass predicted in a recent blog post.

Large September rain events in Seattle have typically topped out at 1.5 inches in terms of single-day totals. Should levels get above that threshold, it could represent a new daily record for the month.

Mass believes this portends even more rain to come in the weeks to come, citing forecast models that show “a lot more coming after this.”

This will be a welcome relief for much of Western Washington, following a summer where the Seattle area experienced a 51-day streak of rain-free days, tying a 1951 mark for the second-most consecutive dry days the city has ever seen. A late-June heat wave also set records for the hottest ever day on record for Seattle, Bellingham, Olympia, and Quillayute, with temperatures at the time ranging between 99 and 108 degrees.

Breakdown of records set during Washington’s heat wave

After a wet weekend, early this week should be drier, KIRO 7 meteorologist Nick Allard notes, “with a little more sunshine.”

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