Mother Nature delivers final sweltering blast before heat dome breaks down

SAN FRANCISCO — After seven days, a heat dome draped over California was finally losing its grip Thursday, but not before delivering one more day of excessive triple digit temperatures away from the coast. 

Livermore has been the poster child of the historic heat wave.  Twice during the week-long onslaught temperatures have climbed to 116 — the hottest ever recorded in the East Bay community.

On Thursday, forecasters predicted record or near high temperatures.

• Santa Rosa —   109  (110 in 1920) 
• Napa           —   102  (108 in 1904)
• Livermore    —   109  (110 in 1944)
• San Jose     —    100 (100 in 1904)
• Gilroy           —    106 (108 in 1957)

 The scorching heat has overwhelmed electrical transformers, knocking out power to thousands. Among those left to sweat out the heat without power were Carly Mueller and her husband Justin.

Thursday was the seventh straight day state power officials have issued a Flex Alert, pleading for conservation. Fortunately, so far no rolling blackouts have been needed to address the record demand.

“With your help, we made it through another day without rotating #poweroutages,” Cal-ISO said on Twitter.

Targeted blackouts were avoided a day after miscommunication led utilities to mistakenly cut power to customers in several California cities.

The confusion occurred Tuesday afternoon between a dispatcher at the Northern California Power Agency, which owns and operates power generating facilities for 16 members including a dozen cities, and the California Independent System Operator as the grid it manages was perilously close to running out of energy amid record-breaking temperatures.

“That is certainly concerning to me,” Elliot Mainzer, president and CEO of Cal-ISO, said Wednesday. “There was a lot happening on the grid for everybody last night. And so we’ll double down on the communication to make sure that doesn’t happen again.” 

Forecasters said cooling coastal marine layer was seen offshore of Big Sur on Thursday and would move up the coast.

“Today will be the last day of hot temperatures with excessive heat warnings and heat advisories in effect until 8 pm Thursday evening,” the National Weather Service said. “Onshore winds and a shallow marine layer will usher in some modest cooling, especially near the coast on Friday though inland areas will be several degrees cooler.”

As the heat exits the state, a new threat from Mother Nature will replace it in Southern California.

Hurricane Kay stayed out in the Pacific on Wednesday as it began lashing Mexico’s Baja California Peninsula, where authorities prepared by opening shelters and closing some roads.

Forecasters said there was a chance outer bands of the big storm could bring heavy rain — and possibly flash floods — to parts of scorched Southern California and southwestern Arizona on Friday night and Saturday.