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California braces for possible power outages as temperatures again break triple digits in relentless heat wave

The heat wave, which started last week, "is historic for both its temperatures and its duration," the state power grid operator said.

California is facing worsening grid challenges and bracing for possible power outages as temperatures again surged into the triple digits Monday.

The California Independent System Operator, or CAISO, which oversees more than three-quarters of the state's electrical power flow, called for residents in a news release "to lower electricity use in the afternoons and evenings to avoid outages" in the historic heat wave.

"We have now entered the most intense phase of this heat wave," the operator's president and CEO, Elliot Mainzer, said at a news conference Monday, giving an update on the heat wave and grid reliability. "Forecasted demand for Monday and Tuesday is at all-time record levels. Potential for rotating outages has increased significantly."

The power system said Monday and Tuesday are projected to be "the most challenging days yet" in the heat wave, "with the highest temperatures forecast on Tuesday and projected electricity demand of 50,099 megawatts."

It issued a “flex alert,” which is a call to conserve energy during critical times, for Monday from 4 p.m. to 10 p.m., “when the grid is most stressed from higher demand and less solar energy” to help avoid outages.

California ended Monday without ordered rotating outages, the system operator said, but it went to an “Energy Emergency Alert 2.” Level 3 is when outages can start to occur, according to its website. It was CAISO’s sixth straight day issuing a flex alert.

As part of the flex alert, residents are encouraged to pre-cool their homes by setting their thermostats to 72 degrees, using appliances like washers and dryers and adjusting curtains to cover windows all before 4 p.m. From 4 to 9 p.m., it is recommended "to set thermostats to 78 degrees or higher, avoid using major appliances, and turn off all unnecessary lights."

Continued calls to reduce energy consumption "are expected as the state endures record-breaking temperatures lasting at least through Friday,” CAISO said.

A map of the U.S. on the National Weather Service website shows that almost the entire state is under an excessive heat warning, meaning there will be "dangerously hot conditions with temperatures over 100 degrees in many locations." The heat warning will remain in effect until Wednesday night.

Image: Intense Heatwave Engulfs Southern California
The National Weather Service issued an excessive heat warning for most of Southern California through Wednesday. Mario Tama / Getty Images

Temperatures are expected to be 100 to 115 degrees across inland areas and in the 80s to 90s closer to the coast, National Weather Service meteorologist Sarah Rogowski said at Monday's news conference.

"We're going to be seeing those values through Thursday and into Friday, especially across the central parts of the valley," she said. "We're also seeing warm overnight low temperatures, also approaching records, just like those high temperatures are each day."

It was 95 degrees in downtown Los Angeles Monday afternoon, and 111 degrees was recorded at Paso Robles Municipal Airport in San Luis Obispo County, according to the National Weather Service.

Bakersfield saw 107 degrees, it was 114 degrees in Sacramento, and 100 degrees was recorded at the airport in Palo Alto in the San Francisco Bay Area.

Heat kills more people annually in the U.S. than other weather disasters, including floods, hurricanes and tornadoes. The National Weather Service recommends drinking plenty of fluids and staying indoors.