According to LA Times, all residents of Calistoga and Geyserville were asked to leave their homes, while mandatory evacuations were conducted in parts of Sonoma Valley.
Meanwhile, California governor Jerry Brown has termed the incident as 'one of the biggest' wildfire in the state's history.
"We’ve had big fires in the past. This is one of the biggest,” he was quoted as saying in the media.
According to officials, Sonoma recorded 13 deaths, while six people died in Mendocino County.
Yuba County and Napa County reported two deaths each.
Almost 115,000 acres (26,000ha) and 3,500 buildings have been destroyed in the blaze.
A state of emergency has been declared in California by its governor, while a disaster declaration has been approved by US President Donald Trump.
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