Previously, California Governor Gavin Newsom announced plans for the regional stay-at-home order to contain the pandemic based on hospital capacity, which is triggered when fewer than 15 percent of beds are available in ICU for a region.
Based on the latest ICU data, the 11-county Southern California region has dropped below 15 percent ICU capacity, the California Department of Public Health (CDPH) said.
The Southern California and the San Joaquin Valley region are home to around 33 million people, which represents 84 percent of the state's population.
In these regions, the new lockdown order will close a wide range of businesses and activities, including bars, breweries, distilleries, wineries, hair salons and barbershops, and personal care services.
Besides, several sectors in these regions, including restaurants, retail, and shopping centers, as well as hotels and lodging, will have additional modifications in addition to 100 percent masking and physical distancing.
Critical infrastructure, schools, and non-urgent medical and dental care can remain open with appropriate infectious disease preventative measures under the terms of the new order.
Authorities urged people to stay at home as much as possible and wearing a face mask when out in public. Residents are also required to keep gatherings small, short, outdoors, and limited to members of one household.
"California is experiencing the fastest increase in cases we have seen yet -- faster than what we experienced at the outset of the pandemic and this summer. If COVID-19 continues to spread at this rate, it could quickly overwhelm our health care system and lead to catastrophic outcomes," officials warned.
As of Sunday morning, California had reported 1,341,700 COVID-19 cases, 19,876 fatalities, and 9,740 people hospitalized, 2,281 of whom are in ICU, according to CDPH data.