Newsom, a Democrat, imposed the nation’s first statewide shutdown in March. His administration developed reopening plans that included benchmarks for virus data such as per capita infection rates that counties needed to meet to relax restrictions.

It released data models state officials use to project whether infections, hospitalizations and deaths are likely to rise or fall.

As cases surged after Thanksgiving, Newsom tore up his playbook. Rather than a county-by-county approach, he created five regions and established a single measurement — ICU capacity — as the determination for whether a region was placed under a stay-at-home order.

In short order, four regions — about 98% of the state’s population — were under the restrictions after their capacity fell below the 15% threshold. A map updated daily tracks each region’s capacity.

At the start of last week, no regions appeared likely to have the stay-at-home order lifted soon because their capacity was well below 15%. But within a day, the state announced it was lifting the order for the 13-county Greater Sacramento area.

Suddenly, outdoor dining and worship services were OK again, hair and nail salons and other businesses could reopen, and retailers were allowed more shoppers inside.

Local officials and businesses were caught off guard. State officials did not describe their reasoning other than to say it was based on a projection for ICU capacity.

State health officials relied on a complex formula to project that while the Sacramento region’s intensive care capacity was below 10%, it would climb above 15% within four weeks. On Friday, it was 9%, roughly the same as when the order was lifted.

“What happened to the 15%? What was that all about?” asked Dr. George Rutherford, an epidemiologist and infectious-diseases control expert at University of California, San Francisco. “I was surprised. I assume they know something I don’t know.”