The blazes have also left at least 180 people injured and have destroyed more than 2,000 homes and businesses.
Described as a "terrible tragedy" by Donald Trump, the President said the US federal government will " stand with the people of California".
Governor Jerry Brown declared a state of emergency for Napa, Sonoma, Yuba, Butte, Lake, Mendocino, Nevada and Orange counties and requested a presidential major disaster declaration to help battle at least 18 blazes burning throughout the state.
A series of fires that flared up north of San Francisco on Sunday night are among the deadliest in the state's history.
Some of the largest of 14 blazes burning over a 200-mile region were in Napa and Sonoma counties, home to dozens of wineries that attract tourists from around the world. They sent smoke as far south as San Francisco, about 60 miles away.
Sonoma County said it has received more than 100 missing-person reports as family and friends scramble to locate loved ones.
The county Sheriff's Office announced two additional deaths there late on Tuesday. That brings the county's total to 11. The other six are spread among Napa, Yuba and Mendocino counties.
Hospitals say they have treated at least 185 people injured by wildfires that have rampaged through parts of northern California since Sunday night.
Most of the injured were taken to Santa Rosa Memorial Hospital's emergency room, which treated about 100 people since the wildfires began.
The hospital said most had respiratory-related issues, including difficulty breathing, asthma and throat irritation, and 14 patients were treated for burns.