The vast region of the U.S. California state will enter a new stay-at-home order on Sunday night, as its many parts have hit the 15 percent or lower threshold for intensive care unit (ICU) capacity amid COVID-19 surge, local health authorities said Saturday.

Based on the latest ICU data, the 11-county Southern California region which includes Los Angeles County, and the San Joaquin Valley region in Central California, have dropped below 15 percent ICU capacity, said the California Department of Public Health in a statement.

It noted that the regional stay-at-home order will take effect in those two regions at 11:59 p.m. Sunday local time (0759GMT) and will remain in effect for at least three weeks.

The Southern California region's ICU capacity has dropped to 12.5 percent as of Saturday, while the available ICU capacity in the San Joaquin Valley region was reported at 8.6 percent on the same day.

The two regions are home to around 33 million people in the most populous state in the United States, representing 84 percent of the state's population, the Los Angeles Times reported.

The other three regions in California, including the Bay Area, Greater Sacramento Region and Northern California region, are also on the brink of new lockdown with ICU capacity hitting 21.7 percent, 21.4 percent and 24.1 percent, respectively.

In response to the recent rapidly increasing number of new cases and hospitalizations from the virus, California Governor Gavin Newsom on Thursday announced plans for the regional stay-at-home order to contain the pandemic based on hospital capacity, which is designed to be triggered when fewer than 15 percent of beds are available in ICU for a region.

The new order will close a wide range of businesses and activities, including bars, breweries, distilleries, wineries, hair salons and barbershops, and personal care services.

In addition, a number of 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.

Public health officials urged people to stay at home as much as possible and wearing a face mask when out in public. Local residents are also required to keep gatherings small, short, outdoors and limited to members of one household.

The California Department of Public Health confirmed 25,068 new cases of COVID-19 and 209 new deaths as of Saturday, bringing the state's total count to 1,311,625 cases and death toll to 19,791.

"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," health officials warned in a daily release.

In Los Angeles, a county home to over 10 million people, Saturday saw 44 newly reported deaths and 8,948 new COVID-19 cases. It is the third consecutive day and the fourth time this week the county's new case number surpassed the previous all-time high.

There are 2,769 people with COVID-19 currently hospitalized in the county, with 23 percent in the ICU. This is more people hospitalized for COVID-19 than at any point during the pandemic and the fifth consecutive day the number of people hospitalized with COVID-19 reached a new all-time high, said the county's Department of Public Health.

"This week, almost 49,000 people tested positive for COVID-19. We can anticipate based on our experience, that 10 percent of newly infected individuals are likely to require hospital care a couple of weeks from now. That translates to close to 5,000 patients, and if even 20 percent of these patients need care in the ICU, they will require 1,000 staffed ICU beds. This is our likely reality in two weeks," said Barbara Ferrer, the county's public health director.

She warned that if residents do not abide by the existing directives, "we are likely to bear witness to one of the worst healthcare crises our county has seen in our lifetime."

Striking a similar note, Los Angeles Mayor Eric Garcetti tweeted on Saturday that "if we don't stop the spread of coronavirus, we could see 3,000 additional deaths in L.A. County, reaching a total of 11,000 dead by the end of the year."