California has returned to the CDC's yellow or "moderate" tier for COVID transmission after a brief return to the orange zone, and now it's the only state in yellow status this week.

The CDC updated its COVID data tracker on Monday, and while much of the country remains in red or "high" status for COVID spread, there are now six states — Connecticut, Illinois, Louisiana, Mississippi, Georgia, and Florida — in the orange or "substantial" tier. California and the territory of Puerto Rico stand alone in the yellow tier.

California was previously in the yellow tier at the beginning of October, and slipped back into the orange tier last week. But we're back at yellow, with a seven-day average of 34.4 new cases per 100,000 residents.

At the county level, there are now three Bay Area counties in the yellow tier: Alameda, Marin, and San Mateo. San Francisco remains in the orange tier, but daily new cases are down 14% this week, and the percent-positivity of cases is down 0.3%, to 1.64%.

Napa has moved out of the red zone and in to the orange, along with the rest of the Bay Area.

Eight Bay Area counties — all but Solano — have agreed to a common set of criteria by which they will be allowed to drop most indoor mask mandates. These criteria include being in the CDC's yellow tier for three consecutive weeks, and having 80% or more of the total population vaccinated. Marin County looks to be the only county that's going to achieve these criteria in the coming weeks.

Last week, San Francisco dropped its mask mandate for workplaces where everyone is vaccinated, and also for gyms, college classes, and religious gatherings. The mandate for public transit, taxis, rideshares, and more come from the state, and those aren't likely to change soon. So, SF and other counties are just waiting for the ability to officially drop masks in bars, restaurants, and retail stores — which may not happen before January, though unofficially, most restaurants, bars, and clubs seem to be letting people go unmasked once inside.

While case counts have been dropping fairly steadily, signs of the next winter surge have been emerging in northern U.S. states as temperatures fall and people move more indoors. Cases have been ticking up in recent weeks across the country's northernmost states, including Michigan, Minnesota, Montana, Wyoming, North Dakota, Idaho, New Hampshire, and Vermont. Some of these states, along with Alaska, have particularly low vaccination rates, but not all of them do. And experts believe this winter's surge will be far less extreme than last year's.