A wind-driven brush fire broke out in Orange County on Monday morning, threatening communities and forcing residents from their homes, amid conditions forecasters were calling the most dangerous fire weather of the year.

The Silverado fire broke out shortly after 6:45 a.m. near Santiago Canyon and Silverado Canyon roads. By 10 a.m., it had burned at least 500 acres, the Orange County Fire Authority said on Twitter.

A mandatory evacuation order was issued for about 60,000 residents in Irvine, including all homes north of Irvine Boulevard between Bake Parkway and Jamboree Road, officials said.

Evacuation centers were being set up at the University Community Center and Quail Hill Community Center in Irvine.

Advertisement

By 8:30 a.m., the fire had crossed the 241 toll road, which was shut down by the California Highway Patrol from Santiago Canyon Road to the 133 toll road.

There was no word on how the fire started. It ignited as parts of Southern California were experiencing fierce, dry Santa Ana winds, with forecasters warning that any fire that were to start could spread rapidly and be difficult to contain.

The National Weather Service issued a red flag warning for Sunday night through Tuesday afternoon amid the conditions, which also threatened more than 120,000 Southern California Edison customers with potential power shutoffs. The warning was in effect for all of Los Angeles and Ventura counties except for the Antelope Valley, as well as the entire Bay Area.

“We have very strong winds and very low humidities, and that’s causing ideal conditions for a very strong Santa Ana event with high fire danger,” said David Sweet, a meteorologist with the National Weather Service in Oxnard. “This is very typical for this time of year, but this one is very strong.”

Advertisement

Wind gusts of up to 80 mph have already led the weather service to upgrade the San Gabriel and San Fernando valleys to high wind warning conditions, noting that a “wave” of winds could crash down into the foothills along the 210 Freeway corridor Monday.

Strong gusts of 60 to 80 mph are also expected in the mountains of Los Angeles and Ventura counties, and 50-mph winds could buffet Malibu and Hollywood Hills. A gale warning has been issued for Catalina Island, and marine officials are being advised to remain in port, seek safe harbor and secure boats and vessels for severe conditions.

The combination of winds and low humidity levels are expected to create “the most dangerous fire weather conditions we have seen since October 2019,” the National Weather Service said.

Advertisement

That month saw the ignition of multiple fires in the region, including the Tick fire, the Easy fire and the Getty fire, which destroyed at least eight homes and caused thousands to flee. The year’s most damaging fire — the Kincade fire in Sonoma County — ignited during an extreme wind event Oct. 23 and subsequently burned through more than 70,000 acres and destroyed more than 300 structures.

Although conditions across Southern California are cooler than they have been in months — the Antelope Valley will see sub-freezing temperatures Monday and Tuesday morning — Sweet said the low humidity is still cause for concern.

“You can be sure that the vegetation is bone-dry and tinder-dry, and so the fire threat is very high for very rapid spread of fire,” Sweet said Monday. “Along with that, you’ve got very strong winds, which means that lit embers and ashes could be carried for miles.”

In response to the increased fire danger across the region, Southern California Edison has warned of public safety power shutoffs that could affect as many as 120,000 customers in six counties, including 24,000 customers in Los Angeles County, 58,000 in San Bernardino County and 13,000 in Orange County.

Advertisement

The preemptive shutoffs come out of concern that wind can damage equipment, creating a spark that might ignite brush and lead to a wildfire.

“Public safety power shutoff is a last resort,” Edison spokesman Ron Gales said. “We only turn off customers’ power when certain thresholds have been breached, and those thresholds are a combination of wind speeds, relative humidity and the preponderance of tinder and dry fuels for fires.”

As of Monday morning, Gales said 29 customers in the Santa Clarita area were without power. Residents should prepare flashlights, write down important phone numbers and review safety plans with family members, among other emergency preparedness tips in anticipation of power shutoffs, he said.

“Some of the most destructive wildfires in the history of Southern California have happened in just the last few months,” Gales said, “so Edison is doing its part to do as much as possible to make sure that our equipment is not involved in the ignition of a catastrophic wildfire.”

Advertisement

Pacific Gas and Electric had said it would cut power to nearly 1 million people in Northern and Central California starting Sunday amid dangerous fire weather. By Monday morning, more than 300,000 customers were without power.

Sweet said people should be ready to take action in the event of a fire.

“Have an evacuation plan in place,” he said, “and if a fire starts near your area and the local authorities advise you to evacuate, please listen to them.”