https://www.mercurynews.com/2021/09/08/dry-lightning-threat-for-bay-area-brings-fire-watch-warning/

Concerns about dry lightning and the potential for more disastrous wildfires loomed over the Bay Area on Wednesday, adding to the anxiety that already has enveloped the region amid a terrible fire season.

The culprit was a monsoon-type system moving up from the Southwest region of the United States.