Restaurant patrons dine outside in downtown Walnut Creek. Restaurants are among the businesses that will be allowed to resume operating outdoors following the state's announcement Monday that it is lifting the coronavirus-related stay-at-home order. (Photo courtesy of Walnut Creek Downtown/Facebook)

California ended its coronavirus-related stay-at-home order for the entire state Monday based on projected intensive care unit populations over the next four weeks.

The ending of the order will move most of the state back into the purple tier of the four-tiered reopening system, allowing businesses like restaurants and hair salons to reopen outdoors.

Gov. Gavin Newsom and state health officials originally implemented the stay-at-home order in December amid a wave of cases caused in part by social gatherings during Thanksgiving.

Regions of the state were placed under the stay-at-home order when their aggregated ICU bed availability fell below 15 percent of the region’s total ICU bed capacity.

While the Bay Area’s ICU availability shot up to 23.4 percent over the weekend, some regions like the San Joaquin Valley and Southern California still have bed availabilities under 2 percent.

According to the state’s Department of Public Health, statewide ICU capacity is projected to be 30.3 percent by Feb. 21, four weeks from Monday. In the Bay Area, it is expected to be 25 percent.

While the state has yet to disclose its exact formula for calculating the projections, Newsom said the data is based on current ICU capacities, viral transmission rates, case rates and a region’s proportion of cases that are admitted to an ICU.

“Everything that should be up is up, everything that should be down is down,” Newsom said Monday during a briefing on the stay-at-home order’s ending, referring to metrics that the state tracks like test positivity rates, case rates and hospitalizations.

“Today, we can lay claim to starting to see some real light at the end of the tunnel,” he added.

The move comes less than a week after state Health and Human Services Secretary Dr. Mark Ghaly suggested the state had weathered the worst of the pandemic’s winter surge and hospitalizations were on a downswing.

“We are seeing some reductions in transmission,” Ghaly said during a briefing last week on the pandemic.

However, Ghaly said Monday he and other state health officials continue to monitor the transmission of new coronavirus variants that may be more easily spread, even when wearing certain types of face coverings.

“We are, of course, concerned about it,” he said. “We’re just getting more familiar with COVID, what it does. The variant creates another unknown and we don’t know enough about it yet.”

With the order’s expiration, all but four counties are now in the purple tier, including the entirety of the Bay Area. Some counties are expected to move to less-restrictive tiers on Tuesday, however, when the state re-examines its tier assignments.

In addition to the stay-at-home order, the state-enforced curfew from 10 p.m. to 5 a.m. expired Monday, allowing non-essential, late-night travel to resume.

Bay Area health officials met Monday’s announcement with little fanfare, urging residents to continue limiting their travel and social gatherings, wearing face coverings and practicing social distancing.

“Under no circumstances should anyone view the state action today as a reason to let down their guard,” Contra Costa County health officer Dr. Chris Farnitano said in a statement.

Contra Costa County’s average number of new COVID-19 cases per day per 100,000 residents continues to sit above 40, according to Contra Costa Health Services.

The county would need to fall below eight new cases per 100,000 to even be eligible to move into a less-restrictive tier.

“We have made progress, but we need to continue what we are doing to keep our families and communities safe,” Farnitano said.

Santa Clara County Health Officer Dr. Sara Cody and Alameda County Health Officer Dr. Nicholas Moss issued similar warnings.

“We may be past the winter surge, but COVID-19 is still with us,” Moss said in a statement. “We are only in the early stages of our vaccination campaign, and the virus has shown us it is capable of returning again and again. That means that, even as we cautiously reopen, we must continue to do the things we know work to keep each other safe.”

Newsom’s announcement was also met with irritation from some state legislators, who claimed they only found out late Sunday evening when the news leaked on Twitter.

“We talked to a lot of folks and we’ve been working with these counties very, very directly for weeks and weeks,” Newsom said. “They’re privy to the same numbers as we are, so we did our best once the data came in and the question is ‘do we delay'” the announcement.

State Republican officials argued Newsom was only acting out of self-preservation and convenience, with a burgeoning recall effort and a fellow Democrat now in the White House.

“This governor’s decisions have never been based on science,” California Republican Party Chair Jessica Millan Patterson said on Twitter. “Him re-opening our state is not an attempt to help working Californians, but rather an attempt to counter the recall movement.”

Newsom laughed off that accusation.

“It’s just complete, utter nonsense,” he said, later adding that the state’s public health decisions are “data-driven, scientifically based (and) not arbitrary.”