The National Weather Service in Sacramento is warning that widespread lightning strikes are possible starting Sunday in parts of Northern California.
The NWS issued a fire weather watch for the Sacramento valley and the Sierra foothills and mountains for late Sunday night through Monday night.
Forecasters say it is too soon to know the track and strength of a weather system expected to arrive Sunday so they can't determine the number and area of lightning strikes.
The weather service says thunderstorms will form over the mountains Sunday afternoon then develop across the valleys Sunday night, with widespread lightning possible.
Several fires in northern California and in Oregon were started by lightning strikes in July.
One of the largest wildfires in California, the Bald Fire in the Lassen National Forest, is 95 percent contained Friday after burning 39,926 acres. The Day Fire in Modoc County was also caused by lightning. It has burned 13,153 acres and is 92 percent contained.
Meanwhile, firefighters are working to contain a lightning-caused wildfire in Siskiyou County that has burned 18,397 acres in the Klamath National Forest. The Beaver Fire started July 30 and is 20 percent contained.