Western Regional Climate Center


August in the West

August saw continued cooler than average temperatures along the Pacific coast with average to record breaking warmth throughout the inland west. Precipitation was low throughout the region, with only weak monsoonal rainfall bringing scattered high precipitation values to some of the Rocky Mountain areas and Southwest states. Drought conditions remain Arizona and New Mexico.

Coastal California continued to see cooler than normal temperatures throughout the month of August due to a persistent marine layer. Santa Barbara, California had an average temperature for the month of 63.8 F (17.6 C), the 7th coolest average on record since 1941. San Francisco airport experienced an average high of 69.4 F (20.8 C), the 7th coolest average monthly high on a record since 1948. Several daily low temperature records were broken or tied along the coast during the month of August.

Except for the Coast, the Southwest saw higher than average temperatures throughout August, with many records being set in southeastern California, Arizona, and New Mexico. On August 9, Roswell, New Mexico experienced a record high of 107 F (41.7 C), beating out the previous record of 103 F (39.4C) in 1951. Tucson, Arizona experienced the second warmest August and summer on record, with an average temperature of 89.3 F (31.8 C). The warmest August on record was in 1994, with an average temperature of 90.2 F (32.3 C). In the last 8 days of August, six high temperature records were tied or broken along with three high minimum temperature records.

The inland Northwest areas experienced average to above average temperatures as well for the month of August. Many high temperature records were set in inland Oregon, Wyoming, Idaho, and Colorado. August 2011 was the hottest on record at Denver, Colorado with an average temperature of 77 F (25 C), beating out the previous record of 76.8 F (24.9 C) set in 1937. Boise, Idaho experienced an average temperature of 78.4 F (25.8 C), the second highest average monthly temperature on record since 1940.

Precipitation was generally lower than average in the West. Numerous locations in the Pacific states received no precipitation at all for the month, where little if any is typically expected. Portland, Oregon reported a monthly total of 0.17 inches (4.3 mm), 0.71 in (18 mm) below the August average of 0.88 in (22.4 mm). At 20% of average rainfall this ranked as the 18th driest July in a 70-year record. Only the far northwestern tip of the Olympic Peninsula received above average rainfall. The rain forest airport at Quillayute received 3.22 in (81.7 mm) on the 22nd, an impressive amount for summer that would receive scant attention in the winter, and ended with 3.27 in (83.1 mm), 131 % of average.

Monsoonal activity favored a few scattered locations in the inland mountainous West, though most were dry. This provided some relief from extreme drought conditions affecting New Mexico, Arizona, and southern Colorado. The monsoon season, mostly now ended, was lighter than usual nearly everywhere in the Southwest except in eastern Utah. Several rainfall records were set early in the month around the Uinta Range of northeastern Utah and southwestern Wyoming and also in southeastern Idaho. On August 2, Idaho Falls received 0.47 in (11.9 mm) of rainfall, breaking the previous record of 0.25 in (6.35 mm) previously set in 1956. Idaho Falls received 1.06 in (26.9 mm) for the month, 150% above the monthly average of 0.7 in (17.8 mm) and the 12th wettest year on record at the location.

Significant Events for August 2011

August 18, Arizona Dust Storm: Strong thunderstorm downdrafts associated with monsoon activity caused a haboob (dust storm) 1,000 feet (305 m) to pass through the Phoenix area. This was the third such notable event to occur in Arizona this summer.

August (all month), Severe drought: The Southwest experienced moderate to exceptional drought during the month of August, with only little relief provided by monsoon rains throughout the month. The severity of the drought was reduced in some parts of New Mexico and Southern Colorado by the end of the month, while drought indices increased for much of Arizona. The drought continues to affect agriculture in the Southwest. Livestock in New Mexico were sold off in large numbers as not enough feed could be grown to sustain the animals.

August 2011 Departure from Normal Temperature and Percent of Normal Precipitation for Western United States

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