Unemployment claims in California have skyrocketed to their highest level in more than a month, officials reported Thursday, a grim sign that coronavirus-linked business shutdowns continue to weaken the state’s frail job market.

California workers filed 158,600 initial claims for unemployment last week, up 20,660 from the prior week, the U.S. Labor Department reported.

The weekly claims totals were the highest since Jan. 9, when 182,600 California workers filed initial claims for unemployment.

Nationwide, workers filed 861,000 initial jobless claims during the week that ended on Feb. 13, up 13,000 from the jobless claims filed the week of Feb. 6.

California is now accounting for a brutally high percentage of the jobless claims filed in the United States.

Despite having only 11.8% of the nation’s labor force, California last week accounted for a jaw-dropping 18.4% of all the unemployment claims filed in the United States, this news organization’s analysis of the weekly jobless filings shows.

Only a few weeks ago, on Jan. 23, California claims represented just 6.3% of the filings nationwide.

For three consecutive weeks since then, California jobless filings have accounted for a sharply increasing share of the filings nationwide. The share was 12.9% on Jan. 30 and 15.3% on Feb. 6, and now is rising towards the 20% mark.

Ominously, the pattern of jobless claims in California points to a rising trend in the number of claims being filed by workers in the state.

During the four weeks that ended on Feb. 13, unemployment claims averaged 114,800 a week, up 10,300 from the average amount for the four weeks ending on Feb. 6. A four-week moving average is used to smooth out week-by-week fluctuations.

Jobless filings have remained at elevated levels since mid-March when state and local government agencies orchestrated wide-ranging business shutdowns to combat the coronavirus.

Even in strong economic times, California workers typically file 40,000 to 50,000 initial unemployment claims every week, noted Michael Bernick, an employment attorney with law firm Duane Morris and a former director of the state Employment Development Department.

“A year ago for the equivalent second week in February 2020, California had 40,392 new claims filed,” Bernick said. “So we’re still way above the pre-pandemic rates.”

The upward trend in jobless filings comes as the state Employment Development Department continues to struggle to pay claims. In addition, the agency is dealing with a wave of fraudulent jobless payments and identity theft.

Spot checks of official notices to the EDD of layoffs show plans for numerous Bay Area businesses to shut their doors for good.

Among the recent notices:

— Stitch Fix is closing permanently in South San Francisco. 162 jobs lost.

— Uniqlo is closing its three-story retail site in San Francisco’s once-robust but now increasingly deserted Union Square. 69 jobs lost.

— Azlo, a financial services tech company based in San Francisco, announced in January it is ceasing operations. 16 jobs lost.

— CSAA Insurance is closing a Fairfield office. 16 jobs lost.

— True Leaf Farms, a produce processing plant, is closing in the Monterey County town of Gonzales. 44 jobs lost.

— Postmates, which was bought by Uber in December, is chopping 69 jobs in San Francisco, although the facility isn’t listed as closing down.

Perhaps the bleakest part of the economic landscape that now confronts California workers who have lost their jobs is many of the businesses they were forced to exit due to the coronavirus shutdowns may no longer exist.

“Thousands of California businesses already have closed permanently,” Bernick said.