211 Connecting Point provides information about rotating power outages / rolling blackouts.

AUGUST 2020 HEATWAVE - During heatwaves, the California Independent System Operator (CAISO), the organization that runs the state’s electric grid, can call for rotating outages statewide to protect the stability of the grid. All utilities in the state – including PG&E have been called on to participate.
https://www.pge.com/en_US/residential/outages/planning-and-preparedness/safety-and-preparedness/find-your-rotating-outage-block/find-your-rotating-outage-block.page

These outages should last between 1 to 2 hours for most customers. These are not Public Safety Power Shutoffs due to extreme fire danger, and are not related to any issues with PG&E’s equipment or its ability to deliver energy locally.

FAQs - https://www.pge.com/en_US/residential/outages/planning-and-preparedness/safety-and-preparedness/keep-power-on.page#faq

California Independent System Operator
http://www.caiso.com/Pages/default.aspx

You can do your part to help prevent blackouts by conserving energy. Set thermostats to 78 degrees or higher. Run energy intensive appliances during early morning or after 9 p.m. Close drapes and blinds to keep rooms cool.