Western Regional Climate Center

PROVIDING CLIMATE SERVICES SINCE 1986

September in the West

Temperatures were mostly above normal throughout the west except for portions of coastal California, the Pacific Northwest and eastern Montana. At Los Angeles Airport it was the coolest September since 1986. At San Diego-Lindbergh Field only 12 days out of 152 (May-Sep) were above the 30-year normal and half of those occurred on the final 6 days of September. It was the 4th coolest May-Sep at San Diego going back 80 years.

Rainfall was well below normal throughout the region except for the Pacific Northwest, Montana and isolated pockets of the Southwest. It was the third wettest September at Seattle dating back to 1948 and second wettest in Olympia. It was very dry across the central Intermountain West. It was the first September in Lander, WY, to record no precipitation dating back to 1948 and in Cheyenne it tied for the driest September (.01”) dating back to 1915. It was the driest September at Pueblo, CO, in 54 years yet only 125 miles southeast in Clayton, NM, it was third wettest September dating back 50 years.

Significant Events for September 2010

September 6-13: Four Mile Canyon Fire, Boulder, CO: This man caused fire 5 miles west of Boulder burned nearly 6,200 acres and destroyed at least 48 homes. Strong winds and dry conditions led to the evacuation of about 3,500 people at one point before the fire was under control.

September 19-26: Machine Gun Fire, Herriman, UT: Machine gun fire at a nearby Army National Guard training camp sparked a wildfire on the 19th that quickly grew to 3,500 acres the next day thanks to hot, dry conditions and 50 mph winds. Roughly 1,600 homes were evacuated and 4 homes were burned.

September 27: Record heat in California: The temperature reached 113 F (45 C) in downtown Los Angeles breaking an all-time record dating back over 100 years. This heat affected all of southern California and broke many records. Even coastal locations reported temperatures of over 100 F (38 C). Nearly 30,000 customers were without power on Monday the 27th as the Los Angeles Department of Water and Power recorded it highest ever demand for electricity.

September (all month): Twitchell Canyon Fire, Utah: This lightning caused fire began July 20th and has grown to over 42,000 acres and was only 28% contained by the end of this month.

September 2010 Departure from Normal Temperature and Percent of Normal Precipitation for Western United States

Departure from normal temperature Departure from normal precipitation

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