An overnight storm brought thunderclaps, lightning and sheets of rain that fell for more than an hour in some parts of the Bay Area on Wednesday night, but the soaking wasn't as severe as it seemed, National Weather Service officials said.

Less than an inch of rain fell in most locations of Contra Costa, Santa Clara and Alameda counties, NWS forecaster Diana Henderson said, and made barely a dent in the ongoing drought. The state's yearly total remains less than 50 percent of normal.

"To be honest, you really wouldn't want to see that much (of the total) made up overnight," she said. "That would be a storm of biblical proportions, and none of us has an ark ready to go."

The NWS said 1.84 inches of rain fell at the 2,400-foot elevation level in Marin County and 1.14 inches fell at Bald Peak at Tilden Park in Contra Costa County between 3 p.m. Wednesday and 3 a.m. Thursday. Those were the only two locations recording more than an inch, Henderson said.

Areas of Oakland received 0.88 inches, the leading total in Alameda County, while the 0.70 inches that fell in Orinda outpaced the rainfall total in the lower elevations of Contra Costa County.

In Santa Clara County, 0.47 inches fell on Mt. Umunhum, but less that two-tenths of an inch fell in San Jose, according to the weather service. Only a quarter-inch fell in San Francisco.


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The storm was at its most intense in central Contra Costa County and parts of the Peninsula, and was responsible for power outages that affected approximately 4,200 people in Martinez, Concord and Clayton. Still, only 0.34 inches fell at Buchanan Field Airport in Concord, Henderson said.

The biggest single outage, according to PG&E spokeswoman Tamar Sarkissian, was caused by a tree falling into a power line at Oak Grove Road and Arbolado Drive in Walnut Creek that kept 3,900 customers in Concord and Martinez without power from 10:47 p.m. on Wednesday until 5:02 a.m. Thursday morning.

The storm departed the Bay Area on Thursday morning, and dry weather was expected until at least Saturday night, when another similar system was expected to hit the Bay Area, Henderson said. That storm is expected to be the last one for a while; Henderson said a high-pressure system is expected to build later in the weekend and push any systems in the Pacific Ocean north of the Bay Area for at least a week.

Contact Rick Hurd at 925-945-4789 and follow him at Twitter.com/3rdERH.