SAN FRANCISCO (AP/CBS13) — Pacific Gas & Electric said Saturday evening it initiated a second round of rolling blackouts impacting up to 220,000 customers as a heatwave baking California in triple-digit temperatures continues to strain the electrical system.

PG&E, which provides electricity to approximately 16 million people in northern and central California, said the blackouts would come between 5 and 10 p.m., and California Independent System Operator (California ISO), which manages the power grid, declared the need for the blackouts at around 6:30 p.m.

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The ISO said in a news release that they declared a Stage 3 emergency, as they did on Friday, due to “increased electricity demand, the unexpected loss of a 470-megawatt (MW) power plant, and loss of nearly 1,000 MW of wind power.”

California ISO said the load was ordered back online just before 6:50 p.m. as wind resources increased.

Locally, thousands of people in Stockton were without power Saturday evening during the blackouts, as police cautioned drivers to be aware that street lights in the city are shut off.

The Stockton Fire Department said approximately 57,000 PG&E customers experienced blackouts but said just after 8:15 p.m. that the utility reported most of those outages were restored.

PG&E shortly after also said all customers had been restored and that they would not call for a public safety power shutoff, as they did during wildfire season in 2019.

PG&E said California ISO directed them Saturday to shut off power for up to 250,000 customers but said they number ultimately resulted in 220,000 affected customers.

The outages affected areas along the central coast and Central Valley, including Monterey, Santa Cruz and San Joaquin counties.

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 move came as temperatures around the state hit triple digits in many areas, and air conditioning use soared.

The power grid is mostly stressed during the late afternoon and early evening because of higher demand and solar energy production falling. The state tried to prepare for the expected rise in electricity use by urging conservation and trying to buy more power. But a high-pressure system building over Western states meant there was less available.

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The state remained gripped by the heatwave Saturday, with several records either tied or broken, according to the National Weather Service.

The last time the state ordered rolling outages was during an energy crisis in 2001. Blackouts occurred several times from January to May, including one that affected more than 1.5 million customers. The cause was a combination of energy shortages and market manipulation by energy wholesalers, infamously including Enron Corp., that drove up prices by withholding supplies.

Counties up and down the state reported scattered outages, although the city of Los Angeles, which has its own power generating system, wasn’t affected.

The heatwave brought brutally high temperatures, increased wildfire danger and fears of coronavirus spread as people flock to beaches and parks for relief. A thunderstorm rolling from the Central Coast to inland Southern California also brought dry lightning that sparked several small blazes, wind and flash flooding in the high desert.

Temperatures were expected to peak above 110 degrees (43 Celsius) in inland regions of state Saturday. The sweltering weather was expected to continue into Wednesday across greater Los Angeles, the Central Valley, Sierra Nevada foothills and parts of the San Francisco Bay Area.

Several cities opened cooling centers, but with limited capacity because of social distancing requirements.

San Francisco’s Department of Emergency Management issued simultaneous tweets urging residents to prepare for power outages and to protect themselves from the coronavirus during the heatwave.

“Stay home when possible. If it feels too hot indoors, seek cooler temps outside, keep physical distance, wear a face covering,” the department tweeted.

The scorching temperatures are a concern for firefighters battling blazes that have destroyed several homes and erupted near rural and urban foothill neighborhoods, driving through tinder-dry brush.

In addition to the possibility of heatstroke and other hot-weather illnesses, health officers were concerned that people will pack beaches, lakes and other recreation areas without following mask and social distancing orders — a major concern in the state that has seen more than 613,000 coronavirus cases.

Israel saw a COVID-19 resurgence after a May heatwave inspired school officials to let children remove their masks, Dr. George Rutherford, an epidemiologist at the University of California, San Francisco, told the San Francisco Chronicle.

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“People will want to take off their masks when it’s hot,” Rutherford said. “Don’t do it.”