Napa County is set to be placed on a state watch list by the California Department of Public Health on Monday, and that means it will have to re-close a number of businesses that have reopened there in the last month.

With its relatively small population and low case count to date — the lowest of any Bay Area County with 436 confirmed cases — Napa was one of the first counties in the region to get the go-ahead to reopen restaurants for indoor dining, as well as movie theaters, museums, and winery tasting rooms. But Monday night the county warned all those businesses to prepare to close again as of midnight on Wednesday (12:01 a.m. Thursday morning).

The reason, as the Napa Valley Register reports, was that the county has just exceeded a state threshold of 100 new cases per 100,000 residents over the previous 14 days. And the announcement came just hours after the county posted a new case total following the holiday weekend, with the single biggest one-day jump in cases that Napa has seen to date, 60. Over the previous two weeks Napa County had recorded 137.9 cases per 100,000 residents.

The businesses that likely must close include bars, breweries, and brewpubs, even if they have outdoor spaces in which to serve. And the closures will last until at least July 30.

Businesses that can remain open include restaurants and wineries for outdoor-only service.

Napa County Supervisor Diane Dillon issued a statement saying, "It is critical that the community continue to follow best practices including wearing a face covering, staying within your household bubble, maintaining a physical distance of at least six feet from those not in your household, and avoiding parties and gatherings. If Napa County cannot improve its metrics, we will likely be subject to an extended closure and additional measures."

Governor Gavin Newsom issued his latest order on July 1, initially listing 19 counties that the state had designated as being on a watch list due to various COVID case metrics. That list has grown to 23 counties as of Monday, with some counties like Santa Clara falling off the list — in that county's case it had to do with its hospitalization rate falling back below 10 percent — and others being added.

In San Francisco, though case counts and hospitalizations have not triggered state monitoring, the decision was made to pause the reopening of indoor restaurants which was scheduled for next week.

The list of counties being actively monitored as of Monday: Colusa, Contra Costa, Fresno, Glenn, Imperial, Kern, Kings, Los Angeles, Madera, Marin, Merced, Monterey, Orange, Riverside, Sacramento, San Bernardino, San Diego, San Joaquin, Santa Barbara, Solano, Stanislaus, Tulare, and Ventura.

Napa has not officially been added to the list, though that appears likely to happen today or tomorrow.

Related: SF Won't Restart Indoor Dining Next Week; No Future Date Set

Photo: Brad Neathery