July in the West
A vigorous onset of the Southwest Monsoon this month provided much needed precipitation and relief from June heat for the desert Southwest and southern Great Basin. June temperature trends continued into July, with coastal regions slightly cooler than normal while inland locations recorded above normal to record-breaking temperatures.
Four monsoonal pushes into the Mojave Desert and southern Great Basin set record precipitation totals throughout the region. Lake Havasu City, Arizona, experienced its wettest July on record at 2.48 in (63 mm). Downpours on the evening of July 13th spurred flash floods in the area that swept away cars, damaged houses, and caused one fatality. Precipitation at Pahrump, Nevada totaled 1.74 in (44.2 mm), the second wettest July in a record dating back to 1914. Near the Nevada/Utah border, Caliente (2.48 in, 63 mm) and Pioche (2.88 in, 73.2 mm), Nevada experienced their third wettest Julys in records dating back to 1903 and 1888, respectively. However, south of there, Las Vegas has recorded less than an inch (0.71 in, 18.0 mm) since October 1, just 20 percent of average. Despite high July precipitation in some locations, by month’s end the USDA had declared natural disaster areas in all Nevada and eastern California counties due to severe and persistent drought. Mid-month, the remnants of Hurricane Fabio traveled northward over California and Nevada up to the Oregon/Idaho/Washington border. The moisture, combined with atmospheric instability, produced light rainfall that set daily records in many locations that typically receive little July precipitation.
Record monthly average temperature was set again this month at Denver, Colorado at 78.9 F (26 C); June 2012 also set the monthly average record at 75 F (23.8 C). Denver experienced 27 days over 90 F (32.2 C) this month, breaking the previous record of 26 days set in 2000 and 2008. Records at Denver date back to 1872. Elsewhere in Colorado, Pueblo experienced 14 days of triple digit (F) temperatures (> 37.8 C) from June 22 through July 5. This shattered the previous record of 9 days. Further south, Beaver Dam, Arizona, recorded its all-time high of 121 F (49.4 C) on July 10. Records at Beaver Dam began in 1951. On the morning of July 12, temperatures at Death Valley, California dropped to a minimum of 107 F (41.7 C), the second highest low temperature since records began in 1911. The record highest low stands at 110 F (43.3 C), set on July 5, 1918.
Further west, temperatures remained slightly below normal throughout July. Southern California saw a smattering of record lows during the last week of the month. The typical summer marine layer affected the California coast throughout the month; the airports at Los Angeles, Santa Barbara, and Monterey all reported 19 days with fog. To the north, Alaska experienced a cool and drizzly July. Average temperature for the month at Anchorage was 55.5 F (13 C), the second lowest July average on a record dating back to 1952.
Significant Events for July 2012
July 14. Montana. Great Falls reported the highest atmospheric water vapor content this location has recorded in all of its weather balloon ascents in a record extending from 1948.
July (all month) Fires throughout the West: Severe fire weather continued for much of the West. These conditions coupled with with numerous thunderstorms this month led to numerous small wildfires and several large fires, described below. The number of fires in the US year-to-date is only 77% of the 10-year average, while the country is at 96% of average in acreage burned.
Oregon: The Long Draw Fire (north of McDermitt, Nevada) and Miller Homestead Fire (1/2 mi, 0.8 km west of Frenchglen, Oregon) both ignited due to lightning on July 8. The Long Draw fire burned 557,648 acres (225,672 hectares) before containment on July 15, by far the largest fire in Oregon’s history. The nearby Miller Homestead fire consumed 160,853 acres (65,094 hectares) before it was contained on July 24. In the past 15 years, 7 of the 11 westernmost states have recorded their largest fire since settlement.
Wyoming: The Arapaho Fire, 28 miles (45 km) northwest of Wheatland, Wyoming, ignited June 27 due to lightning. The fire continued throughout the month of July and at month’s end is 88% contained and burned 98,115 acres (39,705 hectares).
July 31. Las Vegas dry.