He later extended the declaration to include four more northern California counties and Orange County in Southern California.
Sonoma County bore the brunt of the fatalities, with seven fire-related deaths confirmed there, according to the sheriff's department. Two others died in Napa County and one more in Mendocino County, according to the California Department of Forestry and Fire Protection (CalFire).
Details on the circumstances of those deaths were not immediately available from either CalFire or local officials. But KGO-TV in San Francisco, citing unnamed California Highway Patrol officials, described one of the victims as a blind, elderly woman found dead in the driveway of her home in Santa Rosa, a town in Sonoma County.
Two hospitals were forced to evacuate in Sonoma County, state officials said.
Thousands of firefighters battled wind gusts in excess of 50 miles per hour (80 km/h) that have rapidly spread 15 separate wildfires across some 73,000 acres in northern California since erupting late Sunday night, according to CalFire spokesman Daniel Berlant.
About 1,500 homes and commercial buildings have been destroyed throughout the region, Ken Pimlott, director of CalFire, said at a news conference.
A separate wildfire on Monday torched at least a half-dozen homes in the affluent Anaheim Hills neighborhood of Southern California's Orange County, prompting evacuations there, authorities said.
The cause of the fires have yet to be determined, officials said.