The biggest blaze - the so-called Rocky fire north of San Francisco - is reported to be spreading fast and has already consumed more than 90 square miles (145 sq km) of land.
Thousands have been ordered evacuated.
Authorities said some progress had been made in tackling the number of fires, which have been brought down from 21.
At least 24 homes were destroyed as the blaze was whipped up by winds that fuelled the flames, our correspondent says.
"I`ve never seen a fire act like this one," evacuee Vicki Estrella said.
"It`s amazing the way that thing spread. There was smoke 300ft (91m) in the air."
Evacuation advisories have been issued to 13,000 people. More than 6,000 properties currently lie in the path of the flames.
Four years of drought in the western US have left the landscape tinder dry. Coupled with unseasonably humid conditions, lightning strikes and gusty winds, this has posed a severe challenge for fire fighters and water-dropping aircraft.
While some of the reported progress in tackling the blazes has been attributed to the slight fall in temperatures, there is no rain forecast.
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