Updated 12:35 p.m. Tuesday, Aug. 17, 2021.

• GUIDE: How to prepare for a power outage in your home

PG&E says it may shut off power beginning Tuesday night to about 48,000 customers in parts of 18 Northern California counties to prevent its equipment from igniting wildfires amid gusty winds, high temperatures, low humidity and extreme drought conditions.

In the Bay Area, about 6,700 customers could be affected in Napa, Sonoma and Solano counties. Another 350 could have their lights turned off in eastern Contra Costa and Alameda counties.

The potential for what PG&E terms a public safety power shutoff was rated as an "outage watch" on Tuesday, indicating that the utility believes shutoffs are likely.

The National Weather Service's San Francisco Bay Area office on Tuesday tweeted a "dry, gusty offshore flow will develop over the interior North Bay Mountains and East Bay Hills/Diablo Range tonight through midweek," and issued a red flag warning for the region starting Tuesday at 11 p.m. and lasting through 3 p.m. Wednesday. The NWS said winds could gust to 45 mph, with maximum gusts of up to 55 mph at the highest elevations.

PG&E says it began notifying customers Sunday night via text, email and automated phone calls. The company adds that customers can look up their address online to find out whether their location is being monitored for the potential shutoff.

Affected areas lie in the Sierra Nevada foothills, the North Coast, the northern Sacramento Valley and the North Bay mountains.

See the number of customers who may be affected in each county in the table below. Customers enrolled in the Medical Baseline Program, which offers lower energy rates for older people and people with disabilities who need extra power to operate ventilators, dialysis machines or mechanized wheelchairs and may be affected by the shutoffs, are also listed.

PG&E equipment has been responsible for some of the deadliest and most destructive wildfires in modern California history, including the 2018 Camp Fire, which killed 85 people in and around the Butte County town of Paradise.

PG&E said in a report filed with state utility regulators in mid-July that Cal Fire was investigating the company's equipment as the possible cause of the Dixie Fire, which has burned more than 604,000 acres, or about 944 square miles, as of Tuesday morning.

Find more information about PG&E power shutoffs, including KQED's resources on how to prepare for one, here.