S.F. Bay Area records highest-ever temperature

Our reporters are fanning out today to bring you the latest news from around the Bay Area.

Latest updates:

Power grid emergency intensifies

The California grid moves to higher emergency alert level

From 6:30 p.m. to 9 p.m. the California grid will move to Energy Emergency Alert Level 2 — the highest level of emergency so far in this heat wave. If the grid moves through Emergency Alert Level 3, it will turn turn to rolling blackouts as demand overwhelms supply. 

Bay Area school district cuts hours at three schools

Novato Unified School District will run a compressed schedule at Lu Sutton Elementary School, Novato High School and Hill Education Center, schools that have limited or no air-conditioning, during Marin County’s excessive heat warning from Tuesday to Friday. At the high school, each period will be shortened and the school day will finish by 1:15 p.m.

Preliminary heat records shattered across Bay Area

Preliminary high temperatures for the Bay Area’s scorching heat wave are rolling in, and early reports show Livermore possibly soared to 113 to 116 degrees, which would break its daily record high of 108 degrees that was set in 1950. Buchanan Field Airport in Concord tied its all-time record of 112 degrees from 2020, while downtown Oakland reached 100 degrees, breaking its daily record high of 95 degrees in 2008.

The San Francisco Airport tied its daily record high of 93 degrees from 2020. A high of 102 degrees was recorded both at San Jose International Airport and in Mountain View, breaking the previous daily record highs of 99 and 97 degrees in 2009, respectively. Palo Alto reached 98 degrees, breaking the 2008 daily record high of 95 degrees.

The Sonoma County Airport station hit a high of 111 degrees, breaking the 109-degree daily record set two years ago. The Napa County Airport reached 109 degrees, surpassing the 106-degree record in 2020. The National Weather Service Bay Area office will start verifying the records Monday afternoon, but it is unclear when a final report will go out.

Fairfield temps, already at record, could go even higher on Tuesday

Fairfield, in the Travis AFB area, preliminarily recorded a high of 116 degrees — an all-time record for the Bay Area. The city’s temperatures could go higher still on Tuesday, according to Chronicle meteorologist Gerry Diaz. Livermore was another city that saw excruciating temperatures on Tuesday.

California grid declares first stage of emergency for Tuesday

Even as the grid veered toward a power shortage on Monday, officials preemptively declared another emergency on Tuesday from 5 to 9 p.m. Power demand is expected to reach its highest-ever levels on Tuesday, causing the specter of rolling blackouts to linger over California.

Fairfield records Bay Area’s highest-ever temperature

Fairfield hit 116 degrees late Monday afternoon which — assuming the number is finalized by the National Weather Service — would be the highest temperature ever recorded in the nine-county Bay Area, according to Chronicle meteorologist Gerry Diaz. The weather service will begin to verify records on Monday afternoon. The figure was recorded in the vicinity of Travis Air Force Base.

Flex Alert takes effect at 4 p.m.

The California grid operator’s request that Californians reduce their electricity use — a request known as a Flex Alert — is now in effect. Californians are asked to refrain from using energy-hungry appliances such as the dryer or dishwasher, turn out unneeded lights and keep their air conditioning to 78 degrees or higher (85 for those who are not at home). The goal is to prevent rolling blackouts, which could happen if the grid is overtaxed by electricity loads. Regulators have said Monday will be the most challenging day for the grid so far during this heat wave.

Storms possible next weekend

Tropical storm Kay is spinning off the southern coast of Baja California Sur, and is forecast to hit Baja as a hurricane by the middle of the week. Its remnants will bring plenty of moisture into Southern California. This moisture will help spawn scattered wet thunderstorms from San Diego to Santa Barbara, along with portions of Kern County and the Mojave, according to Chronicle meteorologist Gerry Diaz. The latest weather models are signaling that some of this remnant moisture will make it into NorCal next weekend as well. If enough moves in, Northern California could see wet storms as well. But if only sprinkles of remnant moisture move in, the chance for these storms producing dry lightning in the heat-strained forests of Northern California next weekend cannot be ruled out.

Parts of Bay Area see power outages

Up to 5,000 homes and businesses were without power in Napa County, as were more than 5,000 in an area west of Vacaville, according to a PG&E outage map. The utility could not immediately be reached for an explanation, but extreme heat is known to strain all infrastructure, including power equipment. The outages are not part of statewide rolling blackouts, which are a possibility — though not an inevitability — for the late afternoon and evening Monday. 

Callifornia regulators watching for outdoor work violations

Cal/OSHA has told companies in the construction, agriculture, tree-trimming, landscaping, car wash and warehouse fields that it plans to conduct “targeted inspections” to ensure workers safety during the heat wave. By law, employers must supply fresh water, access to shade and regular breaks — and closely monitor employees for signs of heat illness at extreme temperatures.

‘Rolling blackouts are a possibility today,’ grid chief says

The nearly unprecedented strain on the power grid will peak on Monday and Tuesday, with grid officials looking at all possible ways to avert rolling blackouts. The best thing Californians can do, they say, is slash electricity use from 4 p.m. to 10 p.m. on Monday night (and similar hours this week), to offset the immense power demand from air conditioners. Read more here about how the public can help avert blackouts.

Sacramento Valley projected to see record highs of up to 119 degrees

The heat wave in the Sacramento Valley is reaching its apex today and tomorrow, meaning it’s about to experience some of the hottest temperatures seen in the continental United States this year. Weather models are projecting today’s highs reaching 115-119 degrees, according to Chronicle meteorologist Gerry Diaz. Sacramento, Modesto and other cities are forecast to surpass their all-time records the next couple of days. Little overnight heat relief is expected, with nighttime temperatures staying in the 70s, while some of the peaks along the Sierra and Diablo Ranges will likely stay in the 80s overnight. Temperatures will finally drop below 110 degrees in most of the valley by Thursday, but 100-105 degree weather will still be rampant from Thursday to Saturday.

Some BART trains running slower due to the heat:

“There is a 10-minute delay on the Antioch Line in the Antioch and SFO directions due to warm weather conditions,” BART said in its alert feed. The service had also slowed down trains on Sunday for the same reason.

110 degree temperatures coming to Wine Country and the East Bay

Chronicle meteorogist Gerry Diaz reports here on which Bay Area cities are likely to hit 110 on Labor Day.

Don’t go to Stinson Beach, Marin officials warn

“If you are not already at Stinson Beach. …  we’d suggest not going,” the Marin County Sheriff tweeted Sunday. There are “hours-long delays getting into the area, and the parking lots and street side parking is all full.” On Sunday, the sheriff’s office said it had issued more than 145 citations in Stinson Beach. Visitors are requested not to block driveways or park in yards, and to be respectful of residents.

California lawmakers want to rank heat waves

On the desk of Gov. Gavin Newsom is AB2238, a bill that would direct the state’s Environmental Protection Agency to create a ranking system for heat waves by 2025. Hurricanes, earthquakes and even atmospheric rivers get ranked by their severity — so why not heat waves? It’s unclear how the current heat wave would rank, but officials say its extreme temperatures and long duration make it particularly dangerous. Read more here about the heat wave ranking bill, which was passed unanimously with bipartisan support.

‘Too hot to barbecue’

Along the Russian River near Healdsburg — a city expected to see temperatures of 110 degrees on Monday — Myra Perez of Sonoma joked it might be the hottest she’s ever been. Her children, 6 and 3, played in the water, apparently immune to the heat. “It’s too hot to barbecue,” Perez said. “We’re going to In-N-Out. It’s the type of choice many Californians are facing on what is normally an outdoors-oriented holiday.

Parking lots at Marin Beaches and near Golden Gate Bridge area are full

The Golden Gate National Recreation Area tweeteed that parking lots in Stinson Beach, Muir Beach and Rodeo Beach in Marin County are full, as are most of its lots in San Francisco. “We welcome our visitors escaping the heat, and remind them to be patient, get shade, and don’t take chances with cold ocean currents or coastal bluffs,” the park service tweeted.

Even San Francisco is already experiencing ‘extreme’ heat

Heat in San Francisco is considered extreme when it surpasses 85 degrees – and shortly before noon, the downtown reading was already at 89 degrees. The city will remain cooler than most parts of the sweltering region and state, however.

California grid boss says Tuesday demand expected to be highest ever

Amid scorching temperatures across California, the state’s electrical grid operator is forecasting the highest-ever demand for power in state history. Californians burned through 50,270 megawatts of power on July 24, 2006, but California Independent System Operator President and CEO Elliot Mainzer said Monday at a news conference that the expected demand has surpassed that historic high for Tuesday. He called on Californians to conserve their power during the key hours of 4 p.m. to 10 p.m. this week and hoped that those reductions and importing power from other states could get the state through Monday and Tuesday without rolling blackouts.

California grid issues emergency stage 1 notice

In a sign of the intense stress on power supplies caused by the heat wave, the California grid operator has issued an Energy Emergency Alert 1 notice for Monday, effective from 5 p.m. through 9 p.m. This is the first level-1 emergency alert for the grid so far this heatwave, and it is designed to lower power demand from large customers and create more supply. If the grid passes through emergency stages 2 and 3 — something grid officials think could happen Monday — then it is time for rolling blackouts because demand, sent sky-high by air conditioning use, is exceeding supply. Read more here about the nearly unprecedented strain on California’s power grid.

Fire danger is high across California

Officials are warning against any activity that could start a fire, as the extreme temperatures have further dried out vegetation and made it highly vulnerable to a spark. Fire danger is rated high through Friday in most of California. 

How long will the heat wave last?

What feels like an endless heatwave is peaking on this Labor Day, with widespread 105-110° F temperatures coating the North Bay, East Bay and Sacramento Valley. Even San Francisco is getting in on some of the heat wave as parts of the city climb to the 80s today. This historic heat wave isn’t done with California yet. With the heat wave expected to drag out, all excessive heat warnings and advisories for the Bay Area and the Sacramento Valley have been extended through 8 p.m.. Thursday.

Hiker suffering from heat exhaustion rescued from Montara Mountain

Officials rescued a hiker who had experienced heat exhaustion at Montara Mountain in San Mateo County on Sunday, according to a tweet from Cal Fire’s CZU branch. Read here about officials’ warnings about outdoor exertion this weekend, following a string of high-profile heat-related deaths over the past year.

Flex alert in effect Monday from 4 p.m. to 10 p.m.

During that time, electric grid officials are asking Californians to refrain from using energy-intensive appliances such as dryers or dishwashers and turn off unnecessary lights. They also ask people to keep their air conditioning at 78 degrees or higher during that time (pre-cooling your home before 4 p.m. is a good idea). This is the latest in a string of Flex Alerts during the heat wave.

Rolling blackouts a possibility on Monday

Power grid conditions are expected to deteriorate late Monday afternoon as air conditioners work overtime and electricity demand soars. Grid officials anticipate emergency conditions and will ask consumers and businesses to save power from 4 to 10 p.m. in a bid to avert rolling blackouts. Read more here about why grid officials are so worried.

What is a heat wave?

Heat waves are typically defined as unusually hot weather lasting more than two days. But what’s considered unusual can vary across California’s distinct geographical regions. For example, a high of 95 degrees Fahrenheit may describe a normal summer day in the Central Valley. But these temperatures could be unbearable in San Francisco, where residents typically don’t have air conditioning. Weather experts consider these differences when providing warnings about extreme heat. Go here to read more about the science of heat waves.