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A Flex Alert was issued for Friday afternoon as extreme temperatures across California posed a risk to the state’s electric grid.

The statewide Flex Alert will be in place from 4 p.m. to 9 p.m. Friday, in an attempt to avoid power disruptions and rolling blackouts, the California Independent System Operator, which runs most of the state’s electric grid, said in a news release Thursday.

Such conservation would help ease the strain on the grid during the crucial evening hours when solar energy is diminished or no longer available, the agency said.

Flex Alerts are a call to consumers to voluntarily conserve energy when demand for power could outstrip supply, which generally occurs during heat waves when electrical demand is high.

Before the Flex Alert period, residents can: pre-cool the home by lowering the thermostat to 72 degrees; close blinds and drapes to keep the heat out; turn off unnecessary lights; charge mobile devices, laptops, and medical equipment; and use dishwashers, washing machines, and other major appliances.

During the Flex Alert period, the ISO recommends setting the thermostat to 78 degrees or higher; avoiding use of major appliances; turning off unnecessary lights; using fans to cool the home; and unplugging unused items.

If demand still outstrips supply after a Flex Alert is in effect, the ISO said it will use other tools it has available for emergency conditions.

“If those tools are exhausted, the ISO could order California utilities to reduce demand by implementing rotating power outages of relatively short duration to effectively extend the available electricity as much as possible, although that is not anticipated at this time,” the agency said.

Rolling blackouts have become a method for utility companies in the state to intentionally turn off the power when it gets too windy in dry summer months to prevent power lines from toppling and starting wildfires. Such blackouts in August 2020 were the first in nearly two decades caused by an energy shortage.

Temperatures are expected to continue rising across Southern California, with the weekend set to see triple digit heat in some areas. The hottest days will likely be Friday through Sunday, according to the National Weather Service, with the Antelope Valley and the interior San Luis Obispo County expected to see highs of 100 to 112 degrees.

Extreme heat significantly increases the potential for heat-related illnesses, particularly for those working or participating in outdoor activities, the weather service warned.

“Be prepared to drink plenty of fluids, stay in an air- conditioned room, stay out of the sun, and check up on relatives and neighbors,” the NWS cautioned.