Gusty winds combined with hot temperatures and dry air have raised the risk of wildfires to critical levels in parts of California through at least Saturday.
As winds picked up on Thursday morning in the mountains behind Los Angeles and in the Sierra Nevada Range, millions of people across the state braced for stronger, more widespread winds that could whip a single spark into a destructive fire.
Red flag warnings were in effect in portions of Los Angeles and Ventura Counties and along the western side of the Sierra and into the foothills. The warnings mean that experts are worried that fires could start more easily and spread quickly if they do.
Utility companies began shutting off power to tens of thousands of customers to prevent power lines from emitting sparks that could start fires.
The most severe warnings are in Los Angeles and Ventura Counties.
Los Angeles and Ventura Counties were at the center of the fire threat on Thursday. An 81-m.p.h. gust was recorded in the mountains near Six Flags Magic Mountain, 50 miles north of Downtown Los Angeles, on Thursday morning.
“We expect those winds to continue through the day and come down into the valleys,” said Rich Thompson, a meteorologist at the National Weather Service office in Oxnard.
The strongest, most widespread winds in this region were expected on Friday, from the early morning hours into the early afternoon, but the red flag warning was scheduled to continue into Saturday night.
Western Los Angeles County, including Camarillo, Oxnard, Santa Clarita, Simi Valley and Thousand Oaks, was at a particularly high risk because of low relative humidity values and strong sustained winds.
“It’s going to be very dry and pretty warm,” Mr. Thompson said. “It’s one of those days where you need ChapStick and lotion.”
A little to the north, in the mountains of Santa Barbara and San Luis Obispo Counties, red flag warnings were not in effect on Thursday but will be on Friday.
Northern California also has some red flag warnings.
Widespread winds are not expected across the San Francisco Bay Area, though windy weather was unfolding in the mountains nearby; a 60 m.p.h. gust was recorded on Mount St. Helena on Thursday. A red flag warning was in place for the mountains of Sonoma and Napa Counties from Thursday night into Friday morning.
To the north, a portion of Lake County, a rural region about 120 miles north of San Francisco, was under a red flag warning through 2 p.m. Thursday.
A 105 m.p.h. wind gust in the Sierra Nevada.
Winds were already kicking off in the Sierra Nevada. A gust of 105 m.p.h. was recorded at 9,000 feet in Kirkwood ski resort, 40 miles south of Lake Tahoe, on Thursday morning.
Red flag warnings were in effect on the western side of the mountain range, from Mount Lassen in the Cascade Range south along the full stretch of the Sierra, as well as in the neighboring foothills and into some valley areas.
Winds will be strong in San Diego but fire risk is low.
Portions of San Diego, Riverside and Orange Counties were among the places under high wind warnings on Thursday.
Those areas recently received rain from the remnants of a far-off tropical storm, which soaked the ground enough to dampen the risk of fires this week. San Diego recorded an inch of rain, while over three inches soaked the nearby mountains.
Early Thursday, Southern California Edison said it had cut off power to about 40,000 homes and businesses and could potentially do the same another 200,000.
In Central and Northern California, Pacific Gas and Electric had left more than 60,000 customers in the dark already, with more than 20,000 additional outages possible.
Sophia Tavakol said the power was turned off at her condo, in the Oakland Hills near the Caldecott Tunnel, just before 9 a.m. This area was not under a red flag warning, though the Weather Service said the fire threat in the East Bay was “near critical.”
Ms. Tavakol received the message from her homeowners’ association on Wednesday morning that a forced outage was possible. The notice said the outage could last until Saturday.
The fire threat in California is often heightened in September and October, when the light ocean breeze that cools coastal areas often weakens just as winds blowing warm, dry air from the inland deserts can strengthen.
These winds shoot down the western slopes of the Sierra, warming the air beneath them and bringing warmer temperatures along with an increased fire threat.
“Temperatures will be 10 to 20 degrees above normal in the foothills and valleys because of that hot air coming down the western slopes of the Sierra,” said Brent Wachter, a fire meteorologist with the U.S. Forest Service in Redding, Calif.
In Southern California, the winds are known as the Santa Anas. Some of the worst fires in Los Angeles history have burned as fierce Santa Anas blew through the region. During the deadly fires in January 2025, winds reached 100 m.p.h.
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