LOS ANGELES — California’s weather conditions are intensifying after a week of extreme temperatures, prompting fire evacuations in Napa County and sparking a handful of blazes that began burning Saturday morning in the Angeles National Forest.

The Pickett fire broke out Thursday near a remote area in Napa County as weather officials warned about elevated fire threats across the region. The fire quickly spread to 2,133 acres with no containment by Friday morning, forcing hundreds of residents in the small city of Calistoga — known for its wine — to evacuate.

Fire Chief Ryan Isham said crews worked throughout Thursday night, forming a second line of defense along Rattlesnake Ridge to curb the Pickett fire from progressing into Pope Valley. As temperatures warm up, “you will expect to see increased fire activity throughout the perimeter of the fire,” Isham said in a video update to Facebook.

The Pickett fire remained at 3,993 acres with 7% containment until Friday night. By Saturday, the fire spread to 4,690 acres, according to the California Department of Forestry and Fire Protection. About 1,200 fire personnel are currently assigned to the Picket fire, according to Cal Fire.

No structural damages nor injuries were reported, according to Battalion Chief Bob Todeschini. “We’d like to remind everyone to be vigilant and have a plan as we continue with suppression efforts,” he said Thursday in a video statement to X.

New fires emerged this week amid the region’s intense heat wave.

The Little fire in Kern County broke out Friday afternoon, about five miles west of Borel Road. The Little fire burned 300 acres. In Alameda County, the Parks fire burned 113 acres with 75% containment as of Saturday. Smoke plumes were seen spread across the east bay as flames scorched up dry grass.

No evacuation orders were issued for either incident.

A lightning bolt struck a tree and ignited two fires southwest of the Little Rock community, according to a post by the Angeles National Forest on X. A third fire began Saturday morning near Table Mountain, west of Wrightwood. No injuries have been reported.

The National Weather Service has issued a red flag warning for portions of Los Angeles, Ventura, Santa Barbara and San Luis Obispo counties for “an unseasonably hot and unstable air mass capable of producing extreme fire behavior from vertical plume growth [and] low relative humidity.”

The red flag issue will continue until Sunday at 9 p.m. as temperatures are expected to range between 98 and 110 degrees, according to the National Weather Service. Santa Clarita Valley, the San Gabriel Mountains and the Antelope Valley foothills will remain under critical fire warning until Saturday at 9 p.m.

In anticipation of potential fires, the Los Angeles Fire Department has pre-deployed resources dispatched from the state, according to Gov. Gavin Newsom. The dispatch includes: 10 fire engines, two water tenders, two bulldozers, one helicopter, two hand crews, three dispatchers and one Incident Management Team.

A high alert for possible thunderstorms was issued near Pearblossom in the Antelope Valley as of Saturday morning. The storm is expected to move toward Palmdale, Lancaster and Vincent. Residents may experience “sudden strong winds, blowing dust and dangerous lightning.”

“Showers and thunderstorms will be possible over the Los Angeles and Ventura County mountains, and portions of the Antelope Valley, during the afternoon and evening hours through Monday,” the National Weather Service said.

L.A. County is providing cooling centers at several recreation centers and libraries.

“As the Extreme Heat Warning is extended through the weekend, City Departments remain prepared to keep Angelenos safe and respond to any emerging needs,” Mayor Karen Bass said in a statement. “These temperatures can be dangerous – I urge Angelenos to limit their time outdoors if possible, check on your neighbors, and stay cool.”

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