MONTHLY WEATHER SUMMARY
By Jan Null
California State Climatologist, California Department of Water Resources
May 2005

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While Southern California finally dried out with below normal rainfall (though that didn't keep Laguna Hills from succumbing to gravity) the northern half of the state averaged over double their normal rainfall. The rain in the north occurred mostly over the first two-thirds of the month from a series of shortwave troughs embedded in the general West Coast longwave trough pattern that has been a persistent synoptic feature much of the winter and spring. What ridging did occur was short-lived but did result in a few record warm days after the middle of the month.

The combination of a still abundant snowpack, warm weather and up to two inches of rain on May15th and 16th resulted in the Merced River flooding through Yosemite Valley. It peaked at about 13 feet, or a foot above flood level; however that's well short of the 1997 flood which peaked at 23 feet!

A few days later Northern California was drenched by a strong late season storm between May 17th and 19th. The 72-hour storm totals were topped by 9.32 inches at Buck's Lake and 6.35 inches at Brush Creek, both in the Feather River drainage. Blue Canyon reported 5.80 inches, Shasta Dam 4.88 and Venado (above the Russian River) had 4.76 inches. Even at lower elevations the rainfall was memorable with a daily record of 1.39 inches at Red Bluff on the 19th. This rain and the ongoing spring snowmelt pushed many of the north state's rivers and reservoirs to near bankfull. An excellent summary from the CNRFC is online at http://www.wrh.noaa.gov/cnrfc/may2005storms.php .

During May 2005 the 8-Station Precipitation Index in the Northern Sierra received 8.1 inches or 386% of normal for the month making it the wettest May on record for the index. The seasonal total for the 8-Stations is now at 54.3 inches, which is 114% of average to date for the season and 109% for the Water Year.

Overall statewide average temperatures across California for May 2005 were near normal. In general the average maxima were slightly below normal in the north and slightly above normal in the south state while minima statewide were a skosh higher than normal.

A number of daily temperature records were set in May, starting with 89 in El Cajon on the 14th and 105 for Thermal on the 15th. During the period from the 20th through the 24 thre were almost two dozen records set in Southern California. Notable from the list was a Borrego Desert Park with a records of 110 and 112 on the 21st and 22nd. Also on the 21st of May Los Angeles International Airport set a record of 78 degrees while Santa Barbara AP and Camarillo had records of 79 and 85 respectively.


Page last updated 6/14/05.