Counties across Northern California are bracing for a weekend PG&E blackout that could affect hundreds of thousands of people, as the most dangerous fire weather conditions of the year sweep into the Bay Area.

Parts of nearly every zone within PG&E’s territory could be impacted, and county officials on Thursday began issuing estimates for how many customers in their respective regions could be impacted.

The National Weather Service issued a fire weather watch for parts of the North Bay, East Bay, San Francisco Peninsula coast and Santa Cruz mountains, saying it will be the strongest weather event this year and since the 2017 wine country fires.

Dangerous fire weather is expected from Saturday night through Monday morning.

Here’s what we know right now:

• Contra Costa County: The Contra Costa County Fire Protection District warned that 48,000 customer accounts — roughly 150,000 residents — could be without power. The outage is expected to begin at 10 p.m. Saturday and last through at least 2 p.m. Monday.

• Alameda County: The Alameda County Sheriff’s Office tweeted Thursday that an estimated 57,000 customer accounts could be without power starting Saturday at 5 p.m. through Monday, Oct 28 at 2p.m.

• Monterey County: The county’s Office of Emergency Services reported that 664 customer accounts in northern Monterey County could be subject to a 48-hour shutoff beginning Saturday.

Anna Bauman and Dominic Fracassa are San Francisco Chronicle staff writers. Email: anna.bauman@sfchronicle.com dfracassa@sfchronicle.com Twitter: @abauman2 @dominicfracassa