An extended period of unseasonably hot weather impacted Western Washington from the 1st through the 10th of the month. A male berry picker at a farm 1 mile east of Sumas in Whatcom County fell ill on the 3rd and later died.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS SEW wrote it up.
An extended period of unseasonably hot weather impacted Western Washington from the 1st through the 10th of the month. A male berry picker at a farm 1 mile east of Sumas in Whatcom County fell ill on the 3rd and later died. At least 5 other pickers were treated for dehydration.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Seattle, WA wrote its last area forecast discussion before the first event at Aug 1, 7:55 PM PST, 5 minutes earlier.
Area Forecast Discussion
National Weather Service Seattle WA
855 PM PDT Tue Aug 1 2017
.SYNOPSIS...A strong upper level ridge will dominate Western
Washington weather into early next week, keeping the area sunny and
dry. The ridge will induce low level offshore flow through Thursday
which will bring several days of unusually hot weather to Western
Washington. Widespread record highs are likely Wednesday and
Thursday. The ridge will begin to weaken on Friday and move inland
slowly over the weekend for a gradual cooling trend.
&&
.SHORT TERM...The strong upper level ridge over the PacNW has
dropped anchor offshore along roughly 130W this evening, and is
forecast to stay there through Saturday. 500 MB heights over the
area will probably stay around 5910-5920 meters through Thursday
evening before falling to around 5860 meters Saturday morning,
indicating some cooling in the general air mass.
For the short-term the position of the ridge axis offshore will
allow the northerly offshore flow over W WA to become a little more
northeasterly Wednesday and Thursday. This will provide the extra
warming needed to push high temperatures up into the 90s Wednesday
and Thursday. Forecasts remain on track. The hottest day still looks
to be Thursday with some spots S of Seattle reaching 103 degrees. An
Excessive Heat Warning remains in effect through Friday evening for
the interior lowlands from Snohomish County southward. An Excessive
Heat Advisory covers much of the rest of W WA that will get
unusually hot, but not be quite as hot, or for so long, and have
better overnight cooling than the warning area. There could be some
air quality concerns as well which can occur with very hot weather
as ozone and other pollutants increase.
The curve ball in the forecast is all the smoke spreading southward
out of B.C. and S over W WA. The smoke has become prominent on
visible imagery, although most surface visibilities are still around
10 miles or better. The visibility aloft was bad enough that the
arrival rate for flights into Sea-Tac airport was lower, causing
delays. The smoke will filter the incoming sunshine and could
possibly take 1-2 degrees off high temperatures the next couple of
days. Have no fear though we're still doomed to experience the 90s.
Confidence in the forecast for Thursday evening and Friday has
slipped a little. The past several model runs have slowed the
eastward progression of the upper level ridge axis. Now the 18Z run
actually shifts the thermally induced surface trough, that develops
along the coast, inland over W WA on Thursday. This will bring some
shallow cooler westerly flow to the coast sooner, maybe late
Thursday afternoon. This shallow coastal onshore flow weakens
rapidly overnight so that the cooler air may only have a minor
effect over the interior. Between the deflating ridge and weak
shallow onshore flow, temperatures should be a little cooler on
Friday, but should still reach the lower 90s. Kam
.LONG TERM...Previous discussion from the 326 PM AFD...The upper
ridge will weaken and shift inland over the weekend with increasing
low level onshore flow. The models hint at some possible convection
late Sunday over the Cascades but I did not bite on this yet. Expect
some night and morning clouds each day and highs gradually cooling
but still a little above normal.
The upper ridge could actually rebuild slightly over the area
early next week for continued above normal temperatures and
probably less night and morning clouds. Schneider
&&
.AVIATION...Dry northwesterly flow aloft will continue as a strong
upper ridge builds over the area. Surface flow will be northerly and
offshore. The air mass will remain stable and dry with no clouds.
Smoke from wildfires will continue to cause minor visibility
restrictions, mainly aloft, over the next couple of days.
KSEA...VFR with no clouds. Wildfire smoke will continue to be
apparent. Northerly wind 8-12 kt. CHB
&&
.MARINE...Northerly and offshore flow will continue as a thermally
induced trough of low pressure remains over the coast through about
Friday. The flow through the strait will be less than usual.
Northwesterly small craft advisory winds will be possible at times
over the coastal waters, and winds are forecast to remain under 20
kt over the inland waters. CHB
&&
.FIRE WEATHER...An upper level ridge over the western U.S. is
strengthening and a corresponding thermally induced surface trough
is developing north along the Oregon coast into Washington. This
will drive temperatures well above normal and keep the surface flow
northerly or slightly offshore, but light. The warming and drying
will continue through Thursday, which looks to be the peak of this
event with high temperatures approaching all-time records. This
pattern will also result in the overnight thermal belt as well. Warm
nighttime temperatures with poor RH recoveries are anticipated in
the Cascade foothills Tuesday night through Thursday night.
Unstable air aloft will develop tonight through Thursday or Friday,
with a high mid-level Haines of 6 over the mountains and parts of
the lowlands south of the Puget Sound. The combination of hot/dry
weather, with unstable air aloft, in addition to the dry fuels, has
led to development of critical dry and unstable fire weather
conditions. Thus we have Red Flag Warnings over the Cascade and
Olympic mountains. The likelihood is diminished for relative
humidities to drop low enough over the lowlands to warrant a Red
Flag Warning, but there remains a possibility, especially for a
short time in the higher elevations of the south interior on Thursday
afternoon. Hence the Fire Weather Watch remains in place for now.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Excessive Heat Warning until 9 PM PDT Friday for Bellevue and
Vicinity-Bremerton and Vicinity-East Puget Sound Lowlands-
Everett and Vicinity-Hood Canal Area-Lower Chehalis Valley
Area-Seattle and Vicinity-Southwest Interior-Tacoma Area.
Fire Weather Watch from Wednesday afternoon through Thursday
evening for Black Hills and Southwest Interior Lowlands-
Central and South Puget Sound Lowlands-Southeast Puget
Sound Lowlands Generally Below 1500 Feet.
Red Flag Warning until 11 PM PDT Thursday for East Portion of
the Olympic Mountains-West Portion of the Olympic Mountains-
West Slopes of the Central Cascades Generally above 1500
Feet-West Slopes of the North Cascades Generally above 1500
Feet.
Heat Advisory from 11 AM Wednesday to 10 PM PDT Thursday for
Cascades of Pierce and Lewis Counties-Cascades of Snohomish
and King Counties-Cascades of Whatcom and Skagit Counties-
Central Coast-North Coast-Olympics-Western Skagit County-
Western Strait of Juan De Fuca-Western Whatcom County.
PZ...Small Craft Advisory until 5 AM PDT Wednesday for Coastal Waters
From Cape Flattery To James Island 10 To 60 Nm-Coastal
Waters From James Island To Point Grenville 10 To 60 Nm-
Coastal Waters From James Island To Point Grenville Out 10
Nm-Coastal Waters From Point Grenville To Cape Shoalwater
10 To 60 Nm-Coastal Waters From Point Grenville To Cape
Shoalwater Out 10 Nm.
&&
www.weather.gov/seattle
You can see an illustrated version of this discussion at
www.wrh.noaa.gov/sew/gafd/latest_webafd.html1 heat. Local standard time, as filed.
The heat wave resulted in 1 fatality due to heat-related causes, plus five other berry pickers treated for dehydration.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Washington in 2017Every state in 2017This day in weather historyWarnings in Washington, August 2017
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 706935.