California power officials put out a plea: Shut it down at 4 p.m. to protect the grid

Facing a dire forecast of record heat continuing through midweek, a state power official asked the public to observe a Flex Alert that was issued Saturday and extended into Sunday, the fifth consecutive day.

The alternative could be rolling blackouts, said Elliot Mainzer, president and chief executive of the California Independent System Operator, which manages the power grid.

During a Flex Alert, consumers are asked to conserve energy from 4 to 9 p.m., hours when the grid is most stressed.

"When we're in a situation like this, where we're right up against the margin of system capability and you have the kinds of threats to reliability from fires and generation plants coming off line, that consumer flexible demand, that response, can be the difference between the lights staying on or not," Mainzer said during a briefing organized Saturday morning by the state Office of Emergency Services.

Power demand Thursday evening reached its highest level since September 2017, he said.

Multiple generators have been forced out of service due to the extreme heat, making energy supplies tighter. Grid operators are also watching at least two major wildfires threatening transmission lines and power plants in the Los Angeles and San Diego areas.

"These last few days are likely to be a dress rehearsal for what's going to be a considerably more stressed set of conditions as we get into the heart of the weekend," Mainzer said.

The hottest temperatures are still ahead, National Weather Service emergency response specialist Sarah Rogowski said in Saturday's briefing.

Rogowski said record to near-record temperatures were expected early to midweek, in the 80s and 90s along the coast and 100 to 115 in the Central Valley and inland regions of Southern California.

"We are looking at temperatures 10 to 25 degrees above normal for this time of year," Rogowski said. Those will be compounded by unusually high overnight temperatures up to the 90s in some areas of Southern California.

"We're not getting that overnight relief," she said.

Relief will come starting Thursday in the north and then Thursday afternoon and early Friday in Southern California, Rogowski said. Even then, temperatures will remain above normal.

Due to the elevated heat and dryness, California fire officials are positioning forces to respond quickly to new fires or battle a major blaze, said Chris Anthony, chief deputy director of the state Department of Forestry and Fire Protection.

"The hottest and driest days are still ahead of us," Anthony said. "The extreme heat coupled with this persistent drought we're in, as well as the bone dry vegetation, really make for the perfect ingredients for rapid fire spread."

Anthony said there are 4,346 firefighters assigned to active fires in California. Progress made on the Route fire in Castaic, which has burned more than 5,000 acres since Wednesday but was listed as 71% contained Saturday, will allow resources to be drawn to other parts of the state.

In Southern California, temperatures were approaching records midday Saturday in the Antelope Valley and western San Fernando Valley, and slightly higher temperatures were predicted for Sunday, National Weather Service forecaster Kristen Stewart said.

Saturday's high temperatures reached 98 degrees in downtown Los Angeles, 104 in Pasadena, 106 in Van Nuys and 107 in Santa Clarita.

Lancaster was measuring 106 degrees at 12:30, two degrees below the record for the day. Woodland Hills, also at 106, was still well below its record of 114 degrees but was forecast to reach 113 on Sunday.

Along the coast, UCLA reached 90 by midday and Long Beach 97, both several degrees below their records.

Southern California Edison was experiencing an unusual number of heat-related power outages but has been able to restore power quickly, spokesman Ben Gallagher said. Because of the heat, crews were put on standby, equipment was stockpiled and regular maintenance was postponed, he said.

"We're continuing to encourage our customers to conserve," he said.

Californians are strongly urged to lower electricity use by setting thermostats to 78 or higher, health permitting, avoiding use of major appliances, and turning off all unnecessary lights, officials said.

Mark Ghilarducci, director of the Office of Emergency Services, advised the public to stay indoors as much as possible and to use shopping centers or public cooling centers as refuge if outdoors. The locations of 122 cooling centers in Los Angeles County are mapped on the county's website.

This story originally appeared in Los Angeles Times.