All of this is happening in a region where more people are building homes tucked into forests.
What lit these fires in the first place?
Officials are not sure yet.
There were 22 major fires burning in the state on Wednesday, and the specific cause of each fire will be investigated, according to Thom Porter, Southern California region chief at the state’s fire agency.
In general, the vast majority of wildfires are caused by people, Mr. Porter said, and the past few months have been so dry that even seemingly innocuous human activities — a boat-trailer chain dragging on a road, engine heat coming off a car parked in a grassy area — have lit fires. It is possible, he said, that similar things may have started some of the current fires.
Daniel Berlant, assistant deputy director of Cal Fire, the state firefighting agency, said there were no thunderstorms in the region when the fires started, so lightning has been all but ruled out as a cause.
Could it have been downed power lines?
State officials are looking into that possibility. There were some reports of sparking power lines and other electrical equipment problems over the weekend. And poor power-line maintenance by the main utility in Northern California, the Pacific Gas & Electric Company, has been blamed for some past wildfires.
“Power lines are definitely one of the causes we’re looking into,” Mr. Berlant said, adding, “One thing we’ll be looking at is whether the fires started before the lines went down, or after.”