Winds are expected to pick up -- with gusts up to 64mph -- and likely fuel wildfires that have engulfed numerous hillsides in flames, quickly incinerated neighborhoods and prompted the evacuation of more than 110,000 people.
"We stand a fairly good chance of a very challenging night and day (Thursday)," said Tim Chavez, a fire behavior analyst for CalFire, at a news conference on the 90,000-acre Thomas Fire in Ventura County. "There's a lot of potential for some large fire growth (for this fire)."
Overworked firefighters caught a break Wednesday when the winds eased but on Thursday, officials say they will see a "recipe for explosive fire growth" of high winds, a super dry humidity of less than 10% and a fire danger of 296 -- the highest it has ever been.
•More evacuations: Several cities in the Ojai Valley are under mandatory evacuation. Satellite images by the National Weather Service showed the city of Ojai surrounded by fires.
•Areas of concern: Firefighters said they are keeping the Skirball Fire at bay but worry it will jump west of Interstate 405.
•School closures: More than 260 Los Angeles public and charter schools will be closed Thursday and Friday.
•Out-of-state help: About 300 engines are coming from fire departments in other states, Los Angeles County Fire Department Chief Daryl Osby said.
Stretching 140 square miles
The Thomas Fire in Ventura County, which sits just north and west of Los Angeles, grew significantly Wednesday to about 140 square miles.
Officials there said they couldn't give a precise number of homes destroyed, because flames in burned neighborhoods still were too intense for examination. But they had estimated about 150 buildings as of Wednesday night. The number will increase once the focus shifts from firefighting and rescue to more damage assessment, fire officials said.
Airborne embers were irritating firefighters' eyes, said Rich Macklin, a Ventura County fire spokesman.
California Gov. Jerry Brown declared an emergency for the county, freeing state resources such as the National Guard to support response efforts.
The 475-acre Skirball Fire near the tony Bel-Air area of Los Angeles startled morning commuters on Interstate 405.
The busy freeway was shut down over a 9-mile stretch for hours as the fire got closer.
"It was dark until I saw a gigantic ball of orange," I-405 motorist Tiffany Lynette Anderson wrote on Instagram, where she posted a picture of fire raging beside the highway before it was closed.
"I could feel the heat on my windows," said Los Angeleno Joy Newcomb, who also drove by the fire.
The freeway has since reopened, but some ramps remained closed.
Firefighters continued working Wednesday night to keep the fire from jumping west of 405 and battling some flareups, said Peter Sanders, a spokesman for the Los Angeles Fire Department.
Los Angeles authorities ordered parts of the Bel-Air district near the fire to leave, but those are just a fraction of the evacuations that have been ordered in Southern California since Monday night.
Smoke collected even in areas that weren't burning. Health officials warned people in the heavily populated San Fernando Valley and other parts of the northern Los Angeles area to limit their time outdoors.
A video posted to Instagram shows a Los Angeles County Fire helicopter maneuvering around heavy smoke to make a water drop on the Skirball Fire.
The smoke from the fires could be seen from the International Space Station. Astronaut Randy Bresnik wrote in one tweet: "I was asked this evening if we can see the SoCal fires from space. Yes Faith, unfortunately we can. May the Santa Ana's die down soon. #Californiawildfire." In another post he thanked the thousands of people fighting the fires.