SAN FRANCISCO — Pacific Gas & Electric said it planned to cut power Saturday night to about 26,900 customers in the Sierra Foothills as a precaution against accidental wildfire starts.

Affected customers would be in Butte, Yuba, Nevada, El Dorado and Placer counties, the utility said in a statement. That includes portions of Paradise, where a wildfire wiped out nearly 15,000 homes last year.

An additional 1,600 customers in Northern California in Napa, Solano and Yolo counties had their power shut off earlier Saturday but could see it restored soon, after inspections take place to ensure conditions are safe, the utility stated.

A wildfire that started Saturday in Yolo County, called the Sand Fire, burned through 1,700 acres by Saturday night, according to the California Department of Forestry and Fire Protection.

A spokesman for PG&E said it plans to restore many of its customers' power around noon Sunday. PG&E encouraged customers to be prepared for the possibility of losing power by ensuring they have the proper preparations in place.

The warning came as forecasters issued the year's first red flag warning of high fire danger because of strong winds, low humidity and warm temperatures in portions of the Central Valley and areas north of San Francisco.

After downed power lines and PG&E equipment were blamed for previous fires, the utility has been under enormous pressure to avoid another deadly blaze.

Facing lawsuits from insurance companies and wildfire victims, the company filed for bankruptcy protection and replaced many of its top leaders.

Those areas are where the state's most devastating wildfires occurred in the past two years.

"The safety of our customers and the communities we serve is our most important responsibility. We know how much our customers rely on electric service, and our decision tonight to turn off power is to protect our communities experiencing extreme fire danger," Michael Lewis, PG&E's senior vice president of electric operations, said in a statement.

The utility said it considers several factors when determining if power should be turned off for safety. They include periods of excessive winds and low humidity when vegetation is dried out and can easily ignite.

State fire officials said grass and shrub in the valley and foothills have dried despite an unusually rainy spring.

"The moisture stayed with us through May, but it dries out quickly due to our Mediterranean climate," said Scott McLean, a spokesman with the California Department of Forestry and Fire Protection.

The warning is in effect until 5 p.m. Sunday.

Once power is shut off, PG&E said its crews will inspect every de-energized line before they restore power, a process that can keep the lights out for days even after conditions improve.

The precautionary outages could inconvenience customers while endangering some who depend on electricity.

Last week, state regulators approved allowing utilities to cut off electricity when fire risk is extremely high. The California Public Utilities Commission said utilities must do a better job educating and notifying the public, particularly those with disabilities and others who are vulnerable, and ramp up preventive efforts, such as clearing brush and installing fire-resistant poles.