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 three Fahrenheit degrees (1.7 Celsius degrees). Because the temperatures reached in the heat wave are rare in the Pacific Northwest, few residents own air conditioners.