State officials on Tuesday extended a strict stay-at-home order for the Southern California region—a move that was expected as COVID-19 cases continue to mount and the demand on intensive care units continues to exceed their capacity.

The order shutting down most nonessential services and activities went into effect three weeks ago, when the region’s adjusted ICU capacity dipped below 15%. The soonest it could have ended was yesterday, Dec. 28, but that did not happen as hospitals remain overwhelmed by those needing care for the virus.

The order closed personal care businesses like hair and nail salons, banned all personal gatherings and shut down museums and dine-in service at restaurants. The order also limits retail businesses to 20% capacity. Most outdoor recreation—like hiking, biking and fishing—is still allowed but without any mixing among people from different households. Schools already operating under waivers and child care are allowed to stay open.

Many hospitals are already stretching their normal resources and officials are trying to avoid a situation where “not every patient gets the same level of attention that we hope they would,” Dr. Mark Ghaly, state secretary of Health and Human Services, said Tuesday.

If the surge in infections continues to mount, hospitals may have to activate their “crisis care” plans, which can include rationing supplies and staff time, he said.

To try to avoid that end, the governor broke the state into five geographic regions a month ago and tied more restrictive closures to ICU capacity, which began falling perilously low when cases increased shortly after Thanksgiving. That means that nearby counties like Orange, Riverside, Ventura and San Diego also fall under the same rules as Los Angeles County, which has been hit particularly hard by the virus.

Counties can still set more restrictive rules than the state, but they cannot have looser restrictions.

The state will not lift its stay-at-home order on any region until officials project the area’s ICU capacity will recover to 15% within four weeks.

“We essentially are projecting that the ICU capacity is not improving in Southern California and San Joaquin Valley and demand will continue to exceed capacity,” Ghaly said.

To make that prediction, the state looks at four factors: the region’s current ICU capacity, seven-day average of new coronavirus cases, current transmission rates and the current rate of ICU admissions.

Ghaly said the state calculates its projections daily, so extending the stay-at-home order doesn’t necessarily mean it will be in place for another three weeks.

“It could be shorter than that depending on how these four factors come together on a day-over-day basis,” he said.

Right now, the state calculates Southern California’s ICU capacity is still at 0%, although that doesn’t mean zero beds are available. As more ICU beds fill with COVID-19 patients, state officials proactively adjust the regions percentage down in the hope of leaving some room for patients who arrive at hospitals for things like heart attacks, car wrecks and other traumatic injuries.

In simple terms, 0% capacity means regions are “in their surge capacity in the aggregate,” Ghaly said.

Los Angeles County, which accounts for a quarter of California’s nearly 40 million residents, has about 40% of the state’s 24,000 deaths. The county is approaching a milestone of 10,000 deaths. Anyone who has traveled out of Los Angeles County is required to quarantine for 10 days when they return, the health department announced in a news release Monday.

The surge of infections is due in large part to Thanksgiving travel and celebrations, which happened despite warnings from health officials not to gather because the nation’s most populated state was already seeing explosive growth in cases.

Although there are indications more people are heeding stay-at-home orders that apply to all of the state but the northernmost rural counties, there was a bump in air travel in Los Angeles similar to Thanksgiving, with a high of 43,000 passengers on Dec. 23—the highest figure since the start of the pandemic, spokesman Heath Montgomery said.

Gov. Gavin Newsom said Monday that even with admissions to hospitals plateauing in some places, the state was destined to move into a “new phase” that it’s been preparing for as it sets up hospital beds in arenas, schools and tents, though it is struggling to staff them.

“As we move into this new phase, where we brace, where we prepare ourselves for what is inevitable now … based on the travel we have just seen in the last week and the expectation of more of the same through the rest of the holiday season of a surge on top of a surge, arguably, on top of, again, another surge,” Newsom said.

Breaking News Editor Jeremiah Dobruck and the Associated Press contributed to this report.