Governor Gavin Newsom on Monday ordered an immediate halt to all indoor activities at restaurants, bars, entertainment venues, zoos and museums.
In the worst-affected counties of the south-western US state, churches, gyms and hairdressers will also close.
California has more than 330,000 Covid-19 cases, with more than 7,000 deaths.
The reimposition of the restrictions in the state with nearly 40 million people was prompted by a 20% rise in people testing positive in the past two weeks and increasing numbers of Californians are now needing intensive care.
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