Newsom said state officials added four more counties to the list, which tracks spikes in cases and hospitalizations, with a total of 19 counties on the list representing 72% of California's population.
Solano, Merced and Glenn counties were also among the most recent additions to the list.
Orange County has turned into a battleground as two groups debate whether county officials should reinstate the countywide order for wearing face coverings in public.
Newsom emphasized the statewide order requiring the public to wear face coverings in high-risk settings.
Meanwhile, the positivity rate, or the proportion of people being tested that return a positive result for COVID-19, has also gone up to 5.9% over the past seven days. It was 4.4% just a couple weeks ago, the governor said.
"In the last seven days we've seen a 45% increase in the total number of cases that have tested positive in the state of California," he said. "We don't like the trend line and that's why this mandatory mask requirement is in effect and why we're using this dimmer switch to start to pull back."
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As a result of those worsening trend lines, Newsom ordered several counties - Los Angeles, Fresno, San Joaquin, Kings, Kern, Imperial and Tulare - to close bars amid surging COVID-19 cases. He recommended eight other counties, Contra Costa, Santa Clara, Sacramento, Riverside, San Bernardino, Ventura, Santa Barbara and Stanislaus, also close down bars.
Last week the governor instructed Imperial County officials to declare a shelter-in-place order again. The county, which is on the state's border with Mexico, is seeing an exceptionally high positivity rate, or the proportion of people being tested that return a positive result for COVID-19. The 14-day average positivity rate is approaching 23% in Imperial County, Newsom warned.