That looks like a really bad situation! Hospitals evacuated. No info on how the fires started?
I haven’t seen any info other than that the area is really dry now. That is not unusual for CA at the end of summer; in most years, it does not rain in the summer.
Fifty to seventy mph winds may have blown trees into electric grid lines in the rural areas. Bone dry conditions would need only a momentary spark to then ignite dry foliage.