One person has already been found dead at a blaze in the state's north.
Fire drill held at PIMS
Napa, Sonoma and Yuba counties are covered by Governor Jerry Brown's order. The counties are north of San Francisco Bay.
California's fire service said about 49,000 acres (20,000 hectares) have been ravaged by the major infernos in those counties which are famed for their production of wine.
More than a dozen fires are burning in total.
Five women, child burnt alive in Upper Dir house fire
Forest fires are common in the western United States during dry, hot summer months, and can be further fanned by windy conditions.
Last month, a massive fire described as the biggest in the history of Los Angeles forced hundreds to evacuate their homes.
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