https://www.siliconvalley.com/2020/10/21/coronavirus-state-tracker-heres-every-county-tier-assignment-as-of-oct-20/

San Francisco County was the only additional one of California’s 58 counties moved on Tuesday, Oct. 20, to the least restrictive, yellow tier of the state’s coronavirus tracking system.

Counties are assigned to a tier based on metrics showing the speed and the spread of the virus in their borders, and each Tuesday the state updates their status.