LOS ANGELES — California’s most intense heat wave so far this year has arrived, walloping residents with record-breaking temperatures, intensifying wildfires and stretching the state’s electricity supplies.
On Wednesday, temperatures in San Fernando Valley communities north of Los Angeles reached new daily highs of 112 degrees, according to the National Weather Service, while Lancaster, a city in the desert northeast of the city, tied a record of 109 degrees, set in 1948.
Across most of the state, excessive heat warnings were in effect.
Local officials also said that high temperatures and bone-dry conditions were making it difficult to fight the Route fire, which had burned more than 5,200 acres of brush-covered hillsides in the Castaic area of Los Angeles County, prompting evacuation orders and road closures. Crews had begun to contain the fire on Thursday, but seven firefighters had been treated for heat-related injuries, officials said.
“At Barrett Lake, it’s 108 degrees right now, and firefighters are out there fighting this fire,” Nathan Fletcher, chairman of the San Diego County Board of Supervisors, said on Thursday.
For the second day in a row, the state’s grid operator on Thursday pleaded with Californians to save energy from 4 p.m. to 9 p.m. — when the system is the most strained as residents rely on air-conditioners for relief and solar power begins to wane. More so-called flex alerts could come throughout the Labor Day weekend, the agency warned.
Some inland areas could experience even worse heat on Sunday and Monday, according to the National Weather Service. The forecast for Paso Robles in Central California shows temperatures reaching 115 degrees those days.
In anticipation, Gov. Gavin Newsom on Wednesday declared a state of emergency meant to stave off blackouts as Californians began cranking up air-conditioners and fans. The order will formally permit power plants to shift into overdrive and allows the use of backup generators.
“While we are taking steps to get us through the immediate crisis, this reinforces the need for urgent action to end our dependence on fossil fuels that are destroying our climate and making these heat waves hotter and more common,” Mr. Newsom said in a statement.
Though California’s summer had been relatively mild, experts say this heat wave — which meteorologists have predicted will last for a full week — is just the latest manifestation of climate change-driven trends.
Extreme heat has exacerbated the effects of the catastrophic drought plaguing the West by creating more dangerous wildfire conditions and reducing the state’s ability to generate hydroelectric power.
As a result of such compounding crises, leaders in California have for years been scrambling to shore up utility systems not designed for the duration, intensity or frequency of extreme heat.
Policymakers have tried to walk a fine line between tackling the root causes of climate change and addressing immediate emergencies.
Late on Wednesday, California lawmakers approved a wave of aggressive climate measures backed by the governor.
They also moved forward a plan to extend the life of the state’s last nuclear facility, the Diablo Canyon Power Plant, which was scheduled to close its reactors in 2024 and 2025. Mr. Newsom and other leaders have said the state needs the electricity it generates.
