SAN FRANCISCO (AP) — An irate California Gov. Gavin Newsom signed an emergency proclamation allowing some energy users and utilities to tap backup energy sources amid a days-long heatwave that has prompted rolling blackouts affecting hundreds of thousands of households. 

The governor warned that customers could again lose power as early as 3 p.m. Monday as spiking temperatures strain the state's power grid. He didn't say where the outages might occur.

Newsom acknowledged the state failed to predict and plan for the energy shortages.

“I am not pleased with what’s happened," he said during an afternoon press briefing. "You shouldn’t be pleased with the moment that we’re in in the state of California.”

Newsom also sent a letter demanding that the state energy commission, state public utilities commission and the California Independent System Operator investigate broad energy blackouts over two days last week that he said occurred without prior warning or enough time to prepare.

He said residents battling a heat wave and a pandemic in which they're encouraged to stay home as much as possible were left without the basic necessity of electricity.

“These blackouts, which occurred without prior warning or enough time for preparation, are unacceptable and unbefitting of the nation’s largest and most innovative state,” Newsom wrote. “This cannot stand. California residents and businesses deserve better from their government.”

But Steve Berberich, president and CEO of California Independent System Operator, which operates the state's electricity grid, said they have warned the state utilities commission of a resource gap.

“We have indicated in filing after filing after filing that the resource adequacy program was broken and needed to be fixed," he said. “The situation we are in could have been avoided.”

The state Public Utilities Commission did not respond immediately to a request for comment.

Californians packed beaches and river banks over the weekend to cool off from scorching triple-digit temperature that raised the risk of more wildfires and fears of coronavirus spread.

The unusually hot weather overwhelmed the state’s electrical grid, prompting the California ISO to warn of another electricity supply shortage Sunday, though that one was averted.

Residents may not be so lucky this week as Berberich said Monday: “Near certain we’ll be forced to ask the utilities to cut off power to millions today to balance supply and demand. Today and tomorrow and perhaps beyond.”

California ISO ordered the first rolling outages in nearly 20 years on Friday when it directed utilities around the state to shed their power loads. The state’s three biggest utilities — Pacific Gas & Electric, Southern California Edison and San Diego Gas and Electric — turned off power to more than 410,000 homes and businesses for about an hour at a time until the emergency declaration ended 3 1/2 hours later. 

The ISO instituted a second, but shorter, rolling outage Saturday evening that cut power to more than 200,000 customers.

The last time a California governor faced power outages, he was successfully recalled. Gray Davis, a Democrat, was recalled in October 2003 and replaced by Arnold Schwarzenegger, a Republican.

Customers are asked to reduce energy use, especially during peak evening hours, as the hot weather is expected to last through Wednesday night.

California also still faces the threat of power outages to prevent wildfires. Thousands were without power for days last year when Pacific Gas & Electric and other utilities shut off lines amid high, dry winds in order to prevent wildfires.