2009 Pacific Northwest heat wave

The 2009 Pacific Northwest heat wave was a heat wave that affected the Pacific Northwest region of the United States and Canada in late July 2009, particularly areas west of the Cascade Mountains in British Columbia, Oregon and Washington. The heat wave set many new heat records across the area, and broke the previous all-time record-high temperature in Seattle by 3° Fahrenheit (1.7° Celsius). Because the temperatures reached in the heat wave are rare in the Pacific Northwest, few residents own air conditioners.

Temperatures soared to record highs in late July from Medford, Oregon, to Seattle, Washington, and as far north as the Northwest Territories in Canada. The hottest weather occurred from July 26 to August 2, with the peak of the heat from July 28 to July 30. The high of 103 °F (39 °C) at Seattle–Tacoma International Airport on July 29 set the record for the hottest temperature ever in Seattle since records began in 1894, breaking the old record of 100 °F (38 °C) set on July 16, 1941, when the official weather station was located in downtown Seattle, and tied on July 20, 1994, at Seattle–Tacoma International Airport. Nighttime-low temperatures were unusually high as well—in the upper 60s and lower 70s °F (about 21 °C). The morning of July 29, Seattle also set a new record-warmest low temperature, 71 °F (22 °C), breaking the old record of 69 °F (21 °C) set on September 2, 1974, and tied a day earlier on July 28, 2009.

The heat was not confined to Seattle. Portland International Airport in Oregon reached 106 °F (41 °C) on two consecutive days on July 28 and 29, nearly tying the all-time record there of 107 °F (42 °C). Portland tied its warmest low temperature on record with a low of 74 °F (23 °C) on July 28. The neighboring city of Vancouver, Washington, tied its all-time record-high temperature of 107 °F (42 °C) on July 29.

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