The first statewide Flex Alert of the year has been extended through Friday as a punishing heat wave across much of the southwestern U.S. threatens to push California’s electricity supply to the brink.

To mitigate stress on the energy grid and avert power outages, the California Independent System Operator initially issued the alert for 5 to 10 p.m. Thursday, according to an ISO news release.

But on Thursday afternoon, the state’s power grid manager extended the Flex Alert to Friday, when consumers will be again be asked to conserve power, this time from 6 to 9 p.m. ISO officials cited ongoing extreme heat in California and the West as reasons for the decision.

A grid warning was put in place Thursday afternoon, a move that paves the way for the ISO to activate programs to decrease demand.

While the Flex Alert is in place, Californians are urged to keep their thermostat at 78 degrees or higher, use fans to cool the home, turn off unnecessary lights, unplug unused items and avoid using major appliances such as the dishwasher and the clothes washer and dryer.

On top of the measures encouraged by the ISO, residents can do things to prepare for the Flex Alert before it goes into effect. Recommendations include pre-cooling the home by lowering the thermostat before 5 p.m. and closing window coverings, and ensuring electronic devices are already charged.

The grid warning came after 1,100 megawatts of natural gas resources went offline. But plants that were expected to be unavailable came online, and the ISO actually gained about 600 megawatts of power, the agency’s chief operating officer, Mark Rothleder, said in a press briefing.

The operator also got resources from other agencies, including the Los Angeles Department of Water and Power, “and that really helped us,” Rothleder said.

By Thursday evening, the grid was in better shape than officials expected earlier in the day when they extended the Flex Alert into Friday.

“For tomorrow, the load conditions are improving,” Rothleder said, adding that it’s forecast to be aided by slightly cooler temperatures both along the coast and inland.

As of 5 p.m., Rothleder said he expected the state to make it through Thursday with no further energy emergencies or power outages. He noted that conservation efforts were making a difference, and thanked residents for their assistance.

“We know it’s an inconvenience, but at this point we feel like a little bit of inconvenience up front will help us all prevent and collectively help reduce the risk of power outages,” he said.

It’s too early to tell exactly how big an impact conservation had Thursday, but Rothleder said Californians have responded to Flex Alerts by cutting back use by 300 to 500 megawatts.

Southern California had another day sweltering day of extreme heat Thursday, with widespread high temperatures in the 90s and 100s across the region, according to the National Weather Service.

An excessive heat warning remains in place for most of the Southland Thursday.

Rothleder noted that it’s important to conserve while the heat pushes into evening hours as the state loses some energy from solar production, and there’s less hydroelectric power being generated amid the drought.

Still, officials on Wednesday expressed cautious optimism that California’s electrical grid is better off than it was last year, when blistering temperatures forced the first rolling blackouts in the state since the energy crisis 20 years prior. Five Flex Alerts were issued in 2020, compared to three total in the previous two years, according to ISO data.

The state has also taken a number of steps to prevent the possibility of rolling blackouts this year, like obtaining an additional 3,500 megawatts of capacity — including 2,000 megawatts of batteries that can store energy generated from solar and other renewable sources.

However, Elliot Mainzer, ISO’s president and CEO, told state lawmakers last month during an oversight hearing that California is not out of the clear, even with the preventative measures.

“The most significant risk factor for grid reliability remains extreme heat, particularly heat that spreads across the wider western United States. And it continues to get hotter every year,” Mainzer said.