As warm winds and crispy dry conditions continue to create wildfire dangers this week, PG&E has issued an unprecedented warning covering much of Northern California — just not San Francisco or Marin counties.

The latest announcement, made Monday morning, covers 28 California counties in total, and it refers to a "severe wind event" heading for the state on Wednesday and Thursday of this week. Seven out of nine Bay Area counties could be affected, as well as much of the northern central valley, the Sierra, and as far south as Santa Barbara County. Specifics about times of possible shutoffs and the number of customers potentially affected have not been announced and appear as "TBD."

"The main period of weather risk is early Wednesday morning through Thursday midday," says PG&E in a release. "The dry, windy weather pattern is expected to reach from the northern portions of PG&E's service territory and down through the Sacramento Valley before spreading into the central areas of the state including most of the Bay Area."

The shutoff alert area includes parts of Alameda, Alpine, Amador, Butte, Calaveras, Colusa, Contra Costa, El Dorado, Glenn, Lake, Mariposa, Mendocino, Napa, Nevada, Placer, Plumas, San Joaquin, San Mateo, Santa Clara, Santa Cruz, Shasta, Sierra, Solano, Sonoma, Stanislaus, Tehama, Tuolumne, Yolo and Yuba counties.

As the Chronicle notes, of the recent shutoff notices and actual power shutoffs by PG&E, this is far and away the largest and will potentially have the broadest impact on commerce and daily life across a huge swath of the state.

PG&E says that if customers update their contact information here, they will receive a heads-up about shutoffs as they approach. And they're warning people to get their phones and extra phone batteries charged up, to make sure medications that require refrigeration are properly cared for and put in coolers, and to make sure all household flashlights work.

This is basically an earthquake kit situation without the earthquake, and will potentially affect millions of Californians between Wednesday morning and Thursday afternoon.