Stay-at-home orders will take effect in most of California by Sunday, encompassing more than 30 million residents, after hospital capacity dropped to critically low levels in two regions representing the southern half of the state.

The return to strict rules aimed at fighting the coronavirus in the country’s most populous state comes as cases and hospitalizations surge around nationwide, prompting tough new restrictions on the economy and daily life. California has struggled to combat this fall’s viral onslaught despite political will to enact stringent public health measures, and reported more than 25,000 new coronavirus infections Saturday, an all-time single-day high.

Current covid-19 hospitalizations have skyrocketed in the past month, mirroring the rest of the country, as leaders nationwide try to prevent their health systems from being overwhelmed during the holiday season.

In California, intensive care unit capacity in the San Joaquin Valley area, which comprises a dozen counties, has dipped to just 8.6 percent, state health officials announced Saturday. Southern California, which includes 11 counties, is at 12.5 percent. Under a plan announced this week by Gov. Gavin Newsom (D), regions with less than 15 percent capacity must enact a stay-at-home order.

The Bay Area has not yet passed that benchmark, but many of its counties said Friday that they would move ahead with the renewed restrictions, arguing that they must act before hospitals are overwhelmed. Los Angeles County, where 10 million people live, has already enacted its own “safer at home” order banning gatherings with people outside one’s household, with limited exceptions for worship and protesting.

San Francisco Mayor London Breed (D) ordered new lockdowns and business restrictions on Dec. 4 as coronavirus cases surged in the Bay Area. (Reuters)

The rest of the state could follow with stay-at-home measures soon. ICU capacity in the Bay Area is at 21.7 percent, officials said Saturday, while Northern California is at 24.1 percent and the greater Sacramento region is at 21.4.

Under the stay-at-home orders outlined by Newsom, bars, hair salons, barber shops and more must close. Restaurants are limited to takeout or delivery, while retail stores will be limited to 20 percent capacity, and residents are told to stay home for all but essential activities. Schools can remain open.

Spurred by dire predictions from public health experts and dwindling numbers of open hospital beds, officials around the country and across political parties have been turning to new restrictions — travel advisories, business shutdowns and long-avoided statewide mask mandates. Despite high hopes for vaccines that could lead to inoculations for millions of people starting this month, experts have repeatedly warned that grim weeks and months lie ahead.

One new forecast says that fast-tracked coronavirus vaccines will arrive largely too late to spare the United States from a surge in covid-19 deaths. The death toll will probably reach 539,000 by April, according to a Friday estimate from the University of Washington’s Institute for Health Metrics and Evaluation model.

“The vaccine has not come in time to do much about the winter wave,” institute Director Christopher Murray told The Washington Post.

Even with California and the country routinely breaking coronavirus case and hospitalization records, decisions to tighten restrictions on quarantine-weary residents and struggling businesses have drawn pushback, especially after leaders espousing caution were caught flouting their own recommendations, drawing public ire.

Newsom and San Francisco Mayor London Breed (D) went to Napa Valley for birthday dinners last month at the pricey French Laundry, the San Francisco Chronicle reported, while San Jose Mayor Sam Liccardo urged people to stay home for Thanksgiving — then spent the holiday with people from several households.

It is also not clear how rigorously the new orders in California will be enforced. Orange County Sheriff Don Barnes said in a statement Saturday that his office would “remain consistent in [its] approach” and would not respond to reported violations of the rules on face coverings, social gatherings or stay-at-home orders.

“Compliance with health orders is a matter of personal responsibility and not a matter of law enforcement,” Barnes said.

The rules will take effect in the Southern California and San Joaquin Valley regions at 11:59 p.m. Sunday and stay in place at least three weeks. Most of the Bay Area’s orders will take effect Sunday, although Alameda County will wait until Monday and Marin County until Tuesday. The Bay Area’s new rules are set to last through at least early January.

Meryl Kornfield contributed to this report.