SACRAMENTO, Calif. (AP) – Scorching heat pushed California’s electricity supply to the brink Monday as authorities investigated at least 29 possible heat-related deaths, most in the smoldering Central Valley where temperatures reached 115 degrees over the weekend.

An eighth day of intense heat pushed electricity usage to a peak of 50,270 megawatts – a record for California but still short of the 52,000 megawatts experts had predicted for the day.

“It appears we have ridden out this mammoth peak demand without any problems,” said Stephanie McCorkle, spokeswoman for the California Independent System Operator, which manages the state’s power grid. “This was the most strained the system has ever been.”

Meanwhile, utilities in the St. Louis area and New York City labored to restore power to hundreds of thousands whose electricity was knocked out by storms and equipment failures.

Hoping to avoid involuntary rolling blackouts in California, ISO declared a “Stage 2” emergency, which calls for businesses to reduce their power usage in exchange for lower rates. Gov. Arnold Schwarzenegger also directed state agencies to reduce electricity use by 25 percent by turning off unnecessary equipment; he urged local and municipal governments and universities to do the same.

The reductions appeared to work. By 5 p.m. ISO officials said the threat of rolling blackouts had passed.

Tens of thousands of homes and businesses lost power in California on Sunday because of heavy electricity use and high temperatures that caused transformers and other equipment to overheat.

Some 50,000 customers in northern California still were without electricity, including 35,000 in San Jose and the East Bay, according to Pacific Gas & Electric.

About 20,000 Los Angeles customers also remained without electricity.

A nursing home patient in Stockton died from heat-related stress Sunday after the Beverly Healthcare Center’s air conditioning gave out, police said.

In Arizona, authorities said heat may have contributed to the deaths of as many as four men in the Phoenix area over the weekend. The deaths came during a three-day streak of record-breaking temperatures in Phoenix. The temperature soared to 114 degrees Sunday, breaking the record of 112 set in 1906.

The deaths came during three days of record-breaking temperatures in Phoenix. The temperature soared to 114 degrees Sunday, breaking the record of 112 set in 1906.

Meanwhile, in St. Louis, more than 200,000 homes and businesses were still without electricity Monday, down from the more than a half-million that were left in the dark last week after strong storms knocked down power lines. Four deaths in the region were attributed to the storms or the heat.

Ameren Corp. Vice President Richard Mark said Monday that 90 percent of those without power could have the lights back on by Tuesday, with the rest expected to be back up by Wednesday.

The power company has been running TV commercials asking people to be patient. Some 4,000 utility workers from as far away as Arizona are restoring power around the clock, but many customers expressed frustration.

“You’re supposed to have a backup plan in case something like this happens,” said Dana Moorhead, who had no power Monday. “All my food’s gone bad. Just going home is depressing.”

In New York, thousands of Queens residents were facing their second week without power because of a blackout that at one point affected 25,000 customers. By Monday morning, electricity had been restored to about 22,000 of those homes, buildings and businesses, Consolidated Edison said.

The blackout has devastated the inventories of ice cream parlors, bodegas, groceries, butcher shops, fish mongers and restaurants. City officials estimated that at least 750 businesses were affected and said that the losses could reach into the millions of dollars.

At the Thai Pavilion restaurant, tables were set with water glasses and silverware, but the restaurant stood empty while other stores and restaurants started to get power again.

“I’m so jealous of the people who get to open,” said Sam Arjariyawat, who manages the restaurant. “People will have to eat a lot of Thai food … to help us out.”