The worst of the California heat wave has arrived for the final day of Labor Day weekend celebrations, with temperatures expected to reach 110 degrees in St. Helena and Healdsburg. The intense heat prompted warnings about possible power outages on the California power grid on Monday.
What’s behind the scorching temperatures? It’s called a heated dome: an atmospheric lid traps warm air over the western United States, unleashing intense heat. You can read more here about the science of Worsening heat waves in Californiaas the Chronicle weather science team explains.
Our reporters are fanning out today to bring you the latest Bay Area news, and our meteorologist is on hand to talk about what he sees in the future.
Latest updates:
Don’t go to Stinson Beach, Marin officials warn
“If you are not already in Stinson Beach. … we suggest you do not go,” the Marin County Sheriff tweeted Sunday. There are “several-hour delays in entering the area, and the parking lots and street-side parking lots are all full.” On Sunday, the sheriff’s office said it issued more than 145 citations in Stinson Beach. Visitors are asked not to block driveways or park in yards and to be respectful of residents.
California lawmakers want to classify heat waves
On Governor Gavin Newsom’s desk is AB2238, a bill that would direct the state Environmental Protection Agency to create a heat wave rating system by 2025. Hurricanes, earthquakes and even atmospheric rivers are classified according to 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. Find out more here about the heatwave classification bill, which was passed unanimously with bipartisan support.
Parking lots at Marin Beaches and near the Golden Gate Bridge are full
The Golden Gate National Recreation Area tweeted that parking lots at Stinson Beach, Muir Beach and Rodeo Beach in Marin County are full, as are most of its parking lots in San Francisco. “We welcome our visitors who are escaping the heat and remind them to be patient, seek shade and not take chances with cold ocean currents or coastal cliffs,” the park service tweeted.
Dozens of sunbathers swarmed the Bay Area coast Saturday afternoon as temperatures began to warm ahead of an expected heat wave that has state officials worried about heat-related illnesses and potential forest fires.
Greg Griffin/The ChronicleEven San Francisco is already experiencing ‘extreme’ heat
Heat in San Francisco is considered extreme when it exceeds 85 degrees – and shortly before noon the downtown reading was already 89 degrees. However, the city will remain cooler than most of the sweltering regions and state.
California network boss says Tuesday demand expected to be highest on record
Amid scorching temperatures across California, the state’s power grid operator is predicting the highest electricity demand ever in state history. Californians burned 50,270 megawatts of electricity on July 24, 2006, but California Independent System Operator President and CEO Elliot Mainzer told a news conference Monday that expected demand had surpassed that all-time high on Tuesday. He called on Californians to conserve their electricity during key hours from 4 p.m. to 10 p.m. this week and hoped that these cuts and the import of electricity from other states could allow the state to cross Monday and Tuesday without continuous breakdowns.
California Network Issues Stage 1 Emergency Notice
In a sign of intense strain on power supplies caused by the heat wave, the California grid operator issued an Energy Emergency Alert 1 notice for Monday, effective from 5 p.m. to 9 p.m. It s This is the first level 1 emergency alert for the network. so far this heat wave, and it is designed to reduce demand for electricity from large customers and create more supply. If the grid goes through emergency stages 2 and 3 – which grid officials believe could happen on Monday – then it’s time for power cuts, as demand, exaggerated by the use of air conditioning, exceeds the offer. Learn more here about the almost unprecedented strain on the California power grid.
Fire danger is high throughout California
Authorities are warning against any activity that could start a fire, as extreme temperatures have further dried out vegetation and made it highly vulnerable to a spark. The fire danger is high until Friday throughout most of California.
How long will the heat wave last?
What looks like an endless heat wave peaks this Labor Day, with widespread temperatures of 105-110°F blanketing North Bay, East Bay and the Sacramento Valley. Even San Francisco is experiencing some of the heat wave as parts of the city reach their 80s today. This historic heat wave is not over yet with California. With the heat wave expected to continue, all excessive heat warnings and advisories for the Bay Area and Sacramento Valley have been extended until 8 p.m. Thursday.
Fans enjoy the shade as they watch the San Francisco Giants take on the Philadelphia Phillies at Oracle Park in San Francisco on Sunday.
Scott Strazzante/The ChronicleHiker with heat exhaustion rescued from Montara Mountain
Authorities rescued a hiker who suffered from heat exhaustion at Montara Mountain in San Mateo County on Sunday, according to a tweet from the CZU branch of Cal Fire. Read here about officials’ warnings about the outdoor effort 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.
Meanwhile, power grid officials are asking Californians to refrain from using power-hungry appliances such as clothes dryers or dishwashers and to turn off unnecessary lights. They’re also asking people to keep their air conditioning at 78 degrees or higher during this time (pre-cooling your home before 4 p.m. is a good idea). This is the latest in a series of Flex alerts during the heatwave.
A biker rides by Lake Merritt during the Labor Day weekend heat wave in Oakland.
Michaela Vatcheva / Special at The ChroniclePower outages are possible 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 p.m. to 10 p.m. to avoid power outages. Learn more here on why grid officials are so worried.
What is a heat wave?
Heat waves are generally defined as exceptionally hot weather lasting longer than two days. But what is considered unusual may vary across distinct geographic regions of California. For example, a high of 95 degrees Fahrenheit can describe a normal summer day in the Central Valley. But those temperatures could be unbearable in San Francisco, where residents usually no air conditioning. Weather experts take these differences into account when issuing extreme heat warnings. Go here to learn more about the heat wave science.