https://www.siliconvalley.com/2020/10/07/coronavirus-state-tracker-heres-where-every-county-stands-in-the-states-tier-system-on-oct-6/

More California counties moved on Tuesday, Oct. 6, into less-restrictive tiers of the state’s coronavirus tracking system, opening the door for more business and public sectors to reopen or expand their indoor capacities.

Counties are assigned to a tier based on metrics showing the speed and the spread of the virus and every Tuesday the state updates their status. At a minimum, counties have to remain in a tier for three weeks before they can progress on, and they have to meet the next tier’s criteria for at least two consecutive weeks before making a move. They can also backtrack if their performance on the metrics reverses course.