A huge swath of Northern California is bracing for potential widespread blackouts this weekend as a Red Flag Warning fuels fears of fast-moving wildfires and PG&E prepares emergency power shutoffs that could impact thousands of residents.

Officials say the region is facing a volatile mix of strong winds, extremely dry air and brittle vegetation, creating conditions where even a single spark could ignite a major wildfire and spread rapidly.

PG&E said a possible Public Safety Power Shutoff could affect about 7,382 customers across 15 counties, including Alameda, Colusa, Contra Costa, Fresno, Glenn, Lake, Merced, Napa, San Benito, San Joaquin, Solano, Sonoma, Stanislaus, Tehama and Yolo counties, raising the prospect of widespread disruption across multiple communities at once.

San Joaquin County is expected to take the biggest hit with 2,967 customers potentially losing power. Tehama County follows with 1,129 customers at risk, and Glenn County with 971 customers also in the warning zone.

The utility also warned that 296 Medical Baseline customers, people who rely on electricity for critical medical needs, could be impacted if shutoffs are carried out.

“Especially the high winds can blow vegetation, tree branches, into PG&E’s overhead distribution lines and create sparks that could turn into a wildfire,” PG&E spokesperson Megan McFarland told KCRA.

Customers were notified Friday afternoon, roughly 48 hours ahead of any possible shutdowns. PG&E said power could be cut as early as Sunday morning and may remain off into Monday, depending on conditions.