His announcement comes amid a scorching heat wave that has helped spark and spread multiple large blazes, including in Napa, Nevada and Monterey counties, and put a severe strain on the state's power grid, causing California's first rolling blackouts in 19 years.
BAY AREA FIRES: What you need to know about fires burning in Napa, Contra Costa, San Mateo and Alameda counties
Newsom said his declaration was to ensure resources were available for crews battling the fires.
"California and its federal and local partners are working in lockstep to meet the challenge and remain vigilant in the face of continued dangerous weather conditions," he said.
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