MONTHLY WEATHER SUMMARY
By Bill Mork
California Department of Water Resources
July 2004

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A mean upper level trough of low pressure in the eastern Pacific insured enough onshore flow for mostly near to a little above normal July temperatures in California. Preliminary data show the statewide average temperature in July to be 72.4 degrees, 0.6 degree above normal. Area average temperatures ranged from 0.2 degree below normal on the Central Coast to 1.7 degrees above normal in the Sacramento drainage basin.

Cities with the greatest average temperature departures from normal were mostly in Northern California and include plus 4.3 degrees at Burney, plus 3.1 degrees at Adin and Yreka, plus 2.9 degrees at Mount Shasta, plus 2.8 degrees at Quincy, and plus 2.0 degrees at Fresno. Cities with average temperatures well below normal include minus 2.7 degrees at the Santa Barbara Airport, minus 2.5 degrees at Kentfield, and minus 2.2 degrees at the Oakland Museum. June Gloom conditions on the South Coast continued in much of July with 22 days of below normal temperatures in downtown Los Angeles and an average temperature of 1.2 degrees below normal. Riverside had only three days with 100 degrees or higher and an average July temperature of 1.5 degrees below normal. Death Valley recorded the highest temperature for the month on the 26th with 122, still 5 degrees shy of the record for the date.

Very few California cities received any precipitation in July with a statewide average of 0.03 inch, about 11 percent of normal. The Northern Sierra 8-Station Precipitation Index in July picked up 0.04 inch, 20 percent of normal. At the end of July, the Index stood at 46.8 inches, 90 percent of normal to date for the water year ending September 30. This represents 94 percent of the water year normal of 50 inches.

On the first three days of July, an upper level low triggered thunderstorms in the Sierra and northern mountains with 0.56 inch at Manzanita Lake and Yreka, 0.45 inch at Lodgepole, 0.27 inch at Mineral, 0.12 inch at Chester, and 0.06 inch at Bowman Lake. The summer monsoon began on July 8, five days later than average, according to the National Weather Service Office in Tucson AZ. The first good surge of monsoonal moisture plus moisture from dissipated Tropical Storm Blas brought heavy rains to portions of Arizona and to a few locations in Southern California on July 14 - 15. Southland rainfall for that period included 1.02 inches at Descanso in San Diego County, 0.45 inch at Forest Falls in San Bernardino County, and 0.41 inch at Idyllwild in Riverside County with 0.20 inch in 8 minutes. Moisture from Tropical Storm Blas also brought showers to the Central Coast on July 16 with amounts less than a tenth of an inch.

Page last updated 8/9/04.