Historic Seattle heat wave peaks at a record 103 degrees on July 29, 2009.

  • By Peter Blecha
  • Posted 7/30/2009
  • HistoryLink.org Essay 9097

On July 29, 2009, a scorching weeklong heat wave across the Pacific Northwest peaked with record high temperatures being set in various area towns. Seattle reached 103 degrees Fahrenheit for the first time in recorded history while Olympia hit 104 degrees; Kent hit 106 degrees; Winlock hit 110 degrees; and Chehalis hit 111 degrees. Well into a season whose generally sunny weather had already been notable for tying Seattle's driest spell ever recorded -- no measurable rain for 29 days (in May and June, until some showers on June 19th) -- the heat suddenly ratcheted up during the final week of July.

Amid multiple electrical power outages in various places (including Tacoma, downtown Bellevue, and the University of Washington campus) and the sparking of home-threatening brush fires (such as the 600-acre blaze that broke out near Chelan on the 28th), the National Weather Service issued "hazardous weather condition(s)" warnings and "URGENT" air-stagnation advisories ("THE STABLE AIR MASS WILL LIMIT DISPERSION OF OZONE POLLUTANTS AND AIR QUALITY WILL DETERIORATE"). Air-quality warnings were also posted by the Puget Sound Clean Air Agency. 

A Hot Time in the Old Town Tonight 

The Seattle Post-Intelligencer's website noted on the same day that July had already brought seven 90 degree days (including five consecutive days). Most forecasters agreed that daytime highs of 100 or more were on the way.

And it was the rarity of that possibility of reaching triple-digit temperatures which, interestingly, created a minor problem for the KOMO-TV news department. It turns out that their weather forecast graphics were sized for two-digit predictions and the 100 degree forecast for Wednesday the 29th forced some unsightly squeezing to make things fit.

The Old Folks at Home

The National Weather Service also issued their "PRECAUTIONARY / PREPAREDNESS ACTIONS" alert on the 29th:

 "AN EXCESSIVE HEAT WARNING MEANS THAT A PROLONGED PERIOD OF DANGEROUSLY HOT TEMPERATURES WILL OCCUR. THE COMBINATION OF HOT TEMPERATURES AND HIGH HUMIDITY WILL COMBINE TO CREATE A DANGEROUS SITUATION IN WHICH HEAT ILLNESSES ARE LIKELY. DRINK PLENTY OF FLUIDS...STAY IN AN AIR-CONDITIONED ROOM...STAY OUT OF THE SUN...AND CHECK UP ON RELATIVES AND NEIGHBORS."

Ice, Ice baby 

Meanwhile, various other news outlets and blogs joined in by offering further advice for staying cool -- including go swimming or splash in the International Fountain at Seattle Center, see a movie, go hang at a library (the Seattle Post-Intelligencer listed 17 that have AC), linger in your grocery store's frozen food section, put ice-cubes in your shirt, put feet in a bucket of ice, or shower and sit naked in front of an electrical fan.  

All the while, weather watchers -- and other broiled, toasted, and roasted people -- kept eyes on their thermometers in sweaty anticipation that the all-time Seattle heat record of 100 degrees (recorded on July 24, 1994) would perhaps finally be equaled or beaten. The Seattle Times quoted University of Washington meteorologist Cliff Mass on the 29th as confirming that "This is definitely going to be an historic heat wave." That same day KING-TV reported that more than 100 people had lined up prior to Bothell's Home Depot store's 6:00 a.m. opening in the hopes of procuring fans or air conditioners.

A Matter of Degree 

Although the Seattle-Tacoma International Airport's weather station -- which is considered the weather center of record -- recorded Seattle's 103 degrees high at 4:53 p.m., various other sources topped that around town. Boeing Field logged in 104 degrees at 5:53 p.m., the University District's Bartell Drug Store's thermometer scored a blistering 105 degrees at about 3:30 p.m., and The Seattle Times's outdoor thermometer was a blazing 107 degrees a couple hours later. 

Below is a listing intended to show the inexorable climb of Seattle's area daily high temperatures as logged by the Sea-Tac facility:

July 23

  • 69 degrees

July 24

  • 79 degrees 

July 25

  • 86 degrees 

July 26

  • 89 degrees 

July 27

  • 94 degrees 

July 28

  • 97 degrees (NOTE: The overnight low temperature of 71 degrees, at 4:53 a.m., marked the first time in the 64 years of record-keeping that the temperature did not drop below 70 degrees on this date.)

July 29:

  • 103 degrees (NOTE: At about 7 a.m., the temperature was 71 degrees -- marking the highest daily low on record, previously held by a 69-degree degree reading on September 2, 1974.)

Sources: Scott Sunde, "Weather: Heat Wave Ahead," Seattle Post-Intelligencer, July 24, 2009 (http://www.seattlepi.com/); National Weather Service website accessed July 29, 2009 (http://forecast.weather.gov); "Monica Guzman, "How Hot Eill It Be Tomorrow?," Seattle Post-Intelligencer, July 2008, 2009 (http://www.seattlepi.com); Sandi Doughton, "Could Wednesday be Seattle's Hottest Day Ever?," The Seattle Times, July 29, 2009  (seattletimes.nwsource.com); Scott Sunde, "Weather: A Record Day for Heat," Seattle Post-Intelligencer, July 29, 2009 (http://www.seattlepi.com); Puget Sound Clean Air Agency website accessed on July 29, 2009 (http://www.pscleanair.org); "Monica Guzman, "When Will Seattle temperatures break 100 (?," Seattle Post-Intelligencer, July 29, 2009 (http://www.seattlepi.com); Kailani Koenig-Muenster, "Top spots to Cool Off in Seattle," Seattle Post-Intelligencer, July 29, 2009 (http://www.seattlepi.com); "Heat-weary Washingtonians Scramble to Buy Air Conditioners," KING-TV video via Seattle Times July 29, 2009 (seattletimes.nwsource.com); Jack Broom, "Sea-Tac temperature hits 95 -- but Then It Drops to 90," The Seattle Times, July 29, 2009; [11:54 a.m.] (seattletimes.nwsource.com); KING-TV (6:30 p.m.) news broadcast, July 29, 2009; Cliff Mass Weather Blog, website accessed on July 29, 2009 (http://cliffmass.blogspot.com); and author's perspirations and observations.

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