San Francisco, Santa Clara and Napa counties are moving into the red tier.
The three counties are among several that state officials have moved into the red as case numbers and hospitalizations continue to drop.
The news comes after Gov. Gavin Newsom teased on Monday that he expected seven counties in the state to drop into less restrictive tier assignments this week. In addition to the three Bay Area counties, Modoc, Lassen, El Dorado and San Luis Obispo were also downgraded from purple to red.
"Thanks to everyone in our City acting responsibly and doing their part, we can take another step towards reopening and beginning our recovery," said San Francisco Mayor London Breed.
The change means that the counties will be able to reopen indoor dining, gyms, museums and movie theaters. Some outdoor activities like Ferris wheels, carousels and rides can also open and the change increases the types of outdoor sports that will be allowed.
Capacity at indoor businesses like retail stores can also be increased.
San Mateo and Marin counties went from purple to red last week.
Breed encouraged San Franciscans to explore their city and patronize businesses with caution.
"We are still in the midst of a global pandemic," she said. "So that means that for example when you’re at a restaurant waiting for your table, keep your mask on. When your waiter walks up to the table, put your mask on. When you go to the restroom, put your mask on."
The rate of reopening is a careful balancing act.
Experts said that reopening too quickly risks giving rise to another surge.
But Breed is optimistic - if not confident - that as people continue to get vaccinated and cases drop, she will not have to order any more shutdowns.
"I think that we are in a very, very good place to not go backwards. It also is going to be contingent on our behavior," she said.