Pacific Gas & Electric crews work to restore power lines in Paradise, California, Nov. 9, 2018. A U.S. judge overseeing a criminal case against Pacific Gas & Electric Co. asked the utility Tuesday to explain any role it may have played in a massive wildfire that destroyed a Northern California town. Judge William Alsup in San Francisco directed PG&E in a court filing to respond to a series of questions about power line safety and wildfires. Credit: Rich Pedroncelli | AP

In the days before California’s deadliest wildfire erupted near a PG&E Corp. power line during a windstorm, the company kept a close eye on the weather, warned customers it might shut off electricity in the area, and finally decided conditions weren’t bad enough to warrant it, according to a report filed Tuesday with state regulators.

The report from PG&E also shows that the giant utility company made its final decision not to cut electricity more than six hours after the Camp Fire began on Nov. 8 in the Sierra Nevada foothills of Butte County. Pushed by strong winds, the fire leveled the town of Paradise, killing at least 88 people.

Even if PG&E had chosen to cut power, the company wouldn’t have switched off the high-voltage transmission line that malfunctioned in Butte County minutes before the blaze began. That’s because the utility owner’s policy of switching off power when winds kick up applies only to local distribution wires.

The report may nonetheless add ammunition to lawsuits filed against PG&E by residents who lost loved ones and homes, blaming the company’s equipment for starting the fire. No cause has been determined.

Strong winds can snap the wooden poles that support distribution lines, allowing live wires to fall into dry grass, triggering a blaze. Gusts also can cause parallel lines to sway close enough to each other that electrons jump from one to another, causing sparks that can fall into grass.

As wind-driven wildfires increase in the state, California utilities have resorted to shutting off certain power lines during periods of intense winds and low humidity. PG&E had resisted the idea for years but changed course after last year’s devastating wine country fires, which killed 44. State investigators have blamed 17 of those 2017 fires on the company’s equipment.

“We know how much our customers rely on electric service and would only consider temporarily turning off power as a last resort,” Matt Nauman, a spokesman for San Francisco-based PG&E, said in an emailed statement. “By the afternoon of Nov. 8, weather conditions had improved, and PG&E no longer anticipated the need to proactively de-energize.”

Shares of PG&E have plunged 45 percent since the Camp Fire began. After losing more than half its value, the stock has stabilized on speculation state lawmakers may pass legislation to ease the company’s liabilities.

On Oct. 14, PG&E cut electricity to about 60,000 customers during heavy winds, the first time the company had taken that step, according to a separate report. The decision prompted angry complaints from customers, some of whom filed claims against the company for spoiled food and lost business. Before restoring service, however, PG&E found 18 instances of wind damage to its equipment, including tree branches lying on de-energized power lines.

The new report shows that PG&E activated its Emergency Operations Center on Nov. 6 — two days before the Camp Fire began — as forecasts showed the possibility strong winds and very low humidity on Nov. 8. The region had experienced only one rain storm since May, leaving trees and brush dangerously dry.

The forecast called for sustained winds of 20 to 30 miles per hour, with gusts up to 45 miles per hour, bringing with them “a high likelihood of impacts to the company’s equipment and facilities,” according to the report. PG&E alerted several state agencies — including Gov. Jerry Brown’s office and the California Department of Forestry and Fire Protection — and then started warning customers that the power could be cut.

When the windstorm arrived, on Nov. 7, weather conditions never quite reached levels that would warrant turning off electricity, the report shows. By 1 p.m. local time on Nov. 8, winds were starting to diminish, and the company decided that it would not need to deactivate any power lines.

But the Camp Fire had already begun, in the hills east of Paradise. A report PG&E previously filed with the state showed that one of the company’s high-voltage transmission lines malfunctioned 18 minutes before the fire started, with the malfunction happening in the same area where investigators say the flames began. Another, smaller PG&E line nearby malfunctioned 12 minutes after the ignition, according to another report.

The threshold for a power shutoff needs to be “lower than the actual level at which danger would occur,” Michael Wara, director of the climate and energy policy program at Stanford University, said in an interview. “One might imagine that the email exchange ahead of this will likely be subpoenaed,” he said.

The PG&E report doesn’t mention the Camp Fire, instead focusing solely on the company’s decision not to cut power. The California Public Utilities Commission requires utilities to file a report whenever they prepare to shut off electricity for public safety, even if they decide against it in the end.

California regulators have allowed the state’s utility companies to set their own criteria governing which lines they will consider deactivating for safety. While Sempra Energy’s San Diego utility will shut down long-distance transmission lines during windstorms, PG&E and Edison International’s Southern California Edison won’t. Instead, they only de-energize distribution lines, which feed neighborhoods, rural communities or individual homes.

All these choices — which lines to turn off and what weather conditions warrant a blackout — will likely be covered in the lawsuits arising from the fire.

“They obviously have a very difficult decision to make whenever the winds kick up,” said Mike Gatto, a former assemblyman who led the utilities committee. “Do they shut off power for hundreds of customers including medical customers, or do they face second-guessing?”

Gatto said he thought the state could have done everyone a favor by coming up with concrete rules regarding when a utility should shut off power due to increased fire risks. It would eliminate the need for lengthy litigation, he said.

The Camp Fire also prompted a federal court judge in San Francisco on Tuesday to demand assurances from PG&E that its electrical grid hasn’t endangered the public after the company was convicted of safety violations in the wake of a gas pipeline explosion that killed eight people in 2010.

U.S. District Judge William Alsup directed the utility to explain whether its operation and maintenance of power lines could result in local, state or federal criminal charges. PG&E remains on probation after it was slapped in January 2017 with a maximum fine of $3 million by another San Francisco judge who said its crimes in the San Bruno explosion were “very serious and pose great risk to the public safety.”

Bloomberg writer Joel Rosenblatt contributed to this report.