SAN FRANCISCO (CBS/AP) — A blistering holiday-weekend heat wave sent records tumbling across the San Francisco Bay Area Sunday as an “extreme heat storm” maintained its grip on the region.

The high in San Francisco touched the century mark for only the 12th time since record-keeping began in the 1870s, blasting past its previous Sept. 6 record of 92 set in 1904. Both Livermore and Santa Rosa hit 111 degrees before 5 p.m. and an excessive heat warning remained in effect through 9 p.m. for the entire Bay Area.

Downtown Los Angeles reached 111 degrees and a record-shattering high of 121 degrees was recorded in the nearby Woodland Hills neighborhood of the San Fernando Valley. It was the highest temperature ever recorded in Los Angeles County, according to the National Weather Service.

“By our calculations, over 99% of California’s population is under an Excessive Heat Warning or Heat Advisory today,” the weather service in Sacramento tweeted Sunday afternoon.

While some cooling is expected beginning Monday evening, the Bay Area will be experiencing higher than normal temperatures for the rest of the week with a new weather threat approaching.

The National Weather Service issued a Red Flag Wildfire warning from 10 p.m. Monday to 8 a.m. Wednesday. Hot, dry winds will begin to arrive Monday, heightening the chances of new wildfires.

“Winds will shift to the north-northeast and becoming gusty in the North and East Bay Hills by Monday evening and in the Santa Cruz
Mountains by Tuesday morning,” the weather service said. “Locally gusty offshore winds will then continue at times in the North and East Bay Hills and Santa Cruz Mountains through Wednesday morning.”

The exceptionally high temperatures Sunday were also driving the highest power use of the year and transmission losses due to wildfires have cut into supplies. Eric Schmitt of the California Independent System Operator that manages the state’s power grid said up to 3 million customers could lose power for up to four hours Sunday evening.

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Power usage was expected to peak at 6 p.m., and no significant outages had been reported by then.

Cal ISO was projecting a 4,000-megawatt shortfall and urged people to conserve electricity by not using appliances and keeping air conditioners at 78 degrees or above.

“I think it’s fair to say that without significant conservation and help from customers today we’ll have to have some rolling outages,” Cal ISO Vice President Eric Schmitt said.

Pacific Gas & Electric, the state’s largest utility, warned customers that it might cut power starting Tuesday because of expected high winds and heat that could create even greater fire danger. Some of the state’s largest and deadliest fires in recent years have been sparked by downed power lines and other utility equipment.

Gov. Gavin Newsom said the state is taking “aggressive” steps to free electrical capacity and reduce demand.

“California has always been the canary in the coal mine for climate change, and this weekend’s events only underscore that reality,”

Newsom said in a statement. “Wildfires have caused system failures, while near record energy demand is predicted as a multi-state heat wave hits the West Coast for the second time in a matter of weeks.”

Customers are asked to shift the bulk of energy use to late night or early daytime hours.

Steps customers can take include setting air conditioning thermostats to 78 degrees, if health permits; deferring use of major appliances; turning off unnecessary lights; unplugging devices not in use; closing blinds and drapes; using fans when possible; and limiting time the refrigerator door is open

© Copyright 2020 CBS Broadcasting Inc. All Rights Reserved. The Associated Press and Bay City News contributed to this report

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