Governor Gavin Newsom ordered an immediate halt to all indoor activities at places including restaurants, bars, zoos and museums.
In the worst-affected counties of what is America’s most populous state, churches, gyms and hairdressers will also close.
More than 330,000 Covid-19 cases and 7,000 deaths have been recorded in California
Earlier in the pandemic state authorities closed beaches, campgrounds and state parks as it sought to limit interactions of people from different households.
But as data showed the virus was most likely to be transmitted indoors, the Newsom administration began modifying public health orders.
Governor Newsom has repeatedly implored people to refrain from social gatherings and he expressed frustration that many aren’t following the guidance.
“Covid-19 is not going away anytime soon, until there is a vaccine and or an effective therapy,” he said.
“Limit your mixing with people outside of your household. It’s just common sense, but the data suggests not everyone is practicing common sense.”
The city of Los Angeles immediately implemented the mandated shutdowns and Mayor Eric Garcetti said he wouldn’t hesitate to go further.
Earlier this month the city created a colour-coded system to designate the threat level from the virus and corresponding shutdowns.
Rising numbers of cases and hospitalisations now have it at orange — the second-highest designation, when people are to minimise all contact with anyone outside their household.
“Red is when everything shuts down again – everything, to our strictest level. And I do want to warn people that we’re close to that,” Mayor Garcetti said.