Entire Bay Area Under Heat Advisory as Scorching Temperatures Increase Risk of Blackouts, Extreme Fire Danger

This article was updated at 5 p.m. Tuesday.

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Even San Francisco and other typically cooler Bay Area regions sweltered Tuesday amid a brutal heat wave that continued to blanket much of California with record-breaking triple-digit temperatures, as state officials pleaded with residents and businesses to conserve energy to avoid blackouts.

The scorching temperatures have been particularly tough on firefighters as they battle 14 different large blazes around the state. In Northern California, two people were killed by the Mill Fire, which has burned more than 4,000 acres in and around the town of Weed. In Southern California, two people were killed and one was injured by the Fairview Fire, which has burned more than 2,000 acres near the city of Hemet, southeast of Riverside.

Heat advisory expanded to SF and coast

Early Tuesday, the National Weather Service had expanded its heat advisory to include San Francisco, as well as the entire Pacific coastline stretching from Sonoma County to Big Sur. The advisory is in effect through 8 p.m. Tuesday.

San Francisco's downtown and its neighborhoods along the bay could see highs reach into the low 90s Tuesday, before cooling slightly Wednesday but then climbing again Thursday.

Along the coast on the peninsula, temperatures are expected to be in the upper 70s, in the mid-90s in Santa Cruz and in the 80s down the coast in Monterey County. Among the hottest will be in Big Sur, which could reach 102 degrees Tuesday and maintain highs in the 90s through the end of the week.

The service considers these conditions a moderate risk for heat-related illness. This warning encompasses a wide geographic area, including the coastal mountains of Marin County, north Monterey Bay, the northern Salinas Valley, Hollister Valley and Carmel Valley. Highs in these additional areas will range from the upper 80s to the low 100s, with lows falling only into the 60s and 70s through Thursday.

On Tuesday afternoon, the Bay Area Air Quality Management District issued a Spare the Air alert for Wednesday, the fifth straight day the district has issued the alert for unhealthy levels of smog caused by the ongoing heat wave in the region.

“It is a genuinely dangerous event from a human health perspective,” said Daniel Swain, a climate scientist with the University of California, Los Angeles Institute of the Environment and Sustainability.

Meteorologist Jan Null with Golden Gate Weather Services said that while hot weather isn't unusual at this time of year in the Bay Area, the length of the heat wave is rare. The high temperatures afflicting even normally cooler cities like San Francisco, he said, are in part due to a high-pressure system that has prevented greater circulation, or "cut off our natural air-conditioning, the sea breeze."

Inland areas, as usual, are seeing the hottest temperatures, which the service considers an extreme risk for heat-related illness. The areas affected by the most severe temperatures include the interior areas of the North Bay and East Bay, the Santa Clara Valley, the Santa Cruz Mountains, interior Monterey County, southern Salinas Valley and San Benito County.

Overnight lows will likely drop only into the mid- to upper 60s in interior valleys, with 70s and 80s in the hills.

Conservation 'absolutely essential' to avoid blackouts

As people crank up their air conditioners, California officials forecasted record levels of energy use, predicting the electrical load Tuesday evening could top 52,000 megawatts, the highest demand the state has ever seen. Monday's peak demand was 49,020 megawatts.

Elliot Mainzer, president of California Independent System Operators, which runs the state's electrical grid, said the state has additional energy capacity at the moment “but blackouts, rolling, rotating outages, are a possibility.” Mainzer called additional conservation “absolutely essential.”

The CAISO site Tuesday morning showed that California could fall more than 5,000 megawatts short of its power supply at peak demand, forecasted for 5:30 p.m. Tuesday afternoon, CAISO said it expected to declare an Energy Emergency Alert 3 around 5:30 p.m., a procedural move that puts it one step away from ordering rotating power outages. If power reserves are exhausted, the power grid operator says it will order utilities like PG&E to begin rotating outages until the demand meets available supplies.
PG&E had more than 12,000 customers reporting outages around the Bay Area as of shortly before 4 p.m. Tuesday, including more than 8,200 in the East Bay, utility spokesperson Tamar Sarkissian said.

Gov. Gavin Newsom on Tuesday extended an earlier statewide emergency proclamation and an executive order intended to reduce the strain on California's grid and increase the state's energy capacity. Both are in effect through Friday, September 9.

“Californians have stepped up in a big way during this record heat wave, but with the hottest temperatures here now, the risk of outages is real. We all have to double down on conserving energy to reduce the unprecedented strain on the grid,” said Newsom. “We need everyone — individuals, businesses, the state and energy producers — to do their part in the coming days and help California continue to meet this challenge.”

California's energy grid runs on a mix of mostly solar and natural gas during the day, along with some imports of power from other states. But solar power begins to fall off during the late afternoon and into the evening, which is the hottest time of day in some parts of the state. And some of the aging natural gas plants California relies on for backup power aren't as reliable in hot weather.

At CAISO's request on Monday, four temporary emergency power generators deployed by the Department of Water Resources in Roseville and Yuba City were activated for the first time since they were installed last year, providing up to 120 megawatts, enough electricity for 120,000 homes.

CAISO also has issued a Flex Alert call for voluntary conservation between 4 p.m. and 10 p.m. Tuesday, making seven alerts in as many days. Consumers were urged to keep air conditioners at 78 degrees or higher during the period and avoid using major appliances such as ovens and dishwashers.

The efforts have worked to keep the lights on "but we have now entered the most intense phase of this heat wave" that could last into the week, and two to three times the level of conservation will be needed from people and businesses, Mainzer said.

CAISO also issued a Stage 2 Energy Emergency Alert from 6:30 p.m. to 8 p.m. Monday. The second of three emergency alert stages means taking emergency energy-saving measures "such as tapping backup generators, buying more power from other states and using so-called demand response programs," according to a CAISO website. Stage 3 would be rolling blackouts.

Several hundred thousand Californians lost power in rolling blackouts in August 2020 amid hot weather, but the state avoided a similar scenario last summer. Newsom signed legislation on Friday that could allow the state's last remaining nuclear plant to stay open beyond its planned 2025 closure, to ensure more power.

Wildfires turn deadly

The danger of wildfires has grown extreme as scorching heat and low humidity turn brush to tinder. Four deaths were reported over the Labor Day weekend as some 4,400 firefighters battled 14 large fires around California, with 45 new blazes on Sunday alone, said Anale Burlew, a deputy chief with the California Department of Forestry and Fire Protection.

In Northern California, Siskiyou County's Mill Fire was 55% contained Tuesday morning after killing two people, injuring others and destroying at least 88 homes and other buildings since it erupted last week, Cal Fire said. The bodies of the two women, age 66 and 73, were found in the city of Weed on Friday, the Siskiyou County Sheriff's Office announced Monday. Details weren't immediately released.

A few miles away, the Mountain Fire grew to nearly 18 square miles and was only 20% contained, with winds threatening to renew its eastward spread in steep terrain, fire officials said.

In Southern California, two people were killed and one injured by the Fairview Fire, which started Monday near the city of Hemet, the Riverside County Fire Department said. Roughly 50 miles southeast of Los Angeles, the fire quickly spread to at least 2,400 acres, prompting evacuations, and was only 5% contained. Multiple residential structures burned.

The dead people were not immediately identified. Authorities said both were found in the same area but it was not known whether they were from the same household. They were apparently trying to flee when they were overcome.

Ironically, unsettled weather also brought the chance of thunderstorms over Southern California and into the Sierra Nevada, with a few isolated areas of rain but nothing widespread. The storms also could produce lightning, forecasters said, which can spark wildfires.

Scientists say climate change has made the West warmer and drier over the last three decades and will continue to make weather more extreme and wildfires more frequent and destructive.

Cooling centers

Officials in all nine Bay Area counties have opened cooling centers for those looking to beat the heat. In most counties, public libraries are also serving as cooling centers. Find more information at the links below.

• Alameda County
• Contra Costa County
• Marin County
• Napa County
• San Francisco County
• San Mateo County
• Santa Clara County
• Solano County
• Sonoma County

California's state-sponsored cooling center locator is online, and the PG&E website also offers a cooling center locator for Bay Area and Northern California residents.

In San Francisco, S.F. Recreation and Parks announced the city's swimming pools would be free for several hours in the afternoon on both September 6 and 7.

This article includes reporting from The Associated Press and Bay City News.