A widespread power outage was impacting legions of San Francisco residents and businesses Saturday, and it seemed to be a cascading situation that began just before 10 am and extended into evening hours.

A reported 130,000 PG&E customers — which equates to somewhere north of 200,000 residents and business owners, if not 300,000 — were out of power as of Saturday evening, with scant updates available from the utility about when the power may be restored.

As PG&E tells the Chronicle, the trouble began with an outage reported at 9:40 am that was initially just impacting around 14,600 customers in the Inner Sunset, Forest Hill, and neighborhoods around there. Sections of the Richmond and Presidio followed, along with a section of Market Street, around 10:10 am, with around 25,000 customers impacted.

As 0f 3 pm, the Outer Sunset was also impacted, along with parts of Hayes Valley, the Lower Haight, Alamo Square, and the Mission District, and BART and Muni trains were bypassing Van Ness, Civic Center, and Powell stations due to the outage.

The outage was impacting traffic signals across the city, and drivers were being advised to stay off the streets — though this is an unrealistic ask on the last Saturday before Christmas!

An enormous swath of the city remained without power as of 8 pm Saturday, and PG&E suggested that the initial outages were triggered by a fire inside a PG&E power substation

The outage made for some pretty sour grapes for small business owners, especially, on one of the last major shopping and dining days before Christmas, during a season when some businesses make a significant portion of their annual revenue.

Mayor Daniel Lurie jumped on social media to suggest that the city has a handle on the situation, though it is pretty clear this is PG&E's deal, and was not very well handled. And maybe this event will have some impact on a longstanding push from the Board of Supervisors to divorce the city from PG&E's grid. But we'll see!!

This is a developing story.