Pacific Gas & Electric implemented a controversial practice of cutting power to selected portions of Northern California on Saturday to guard against wildfires as the weather turned very windy, dry and hot.

Electricity was turned off around 6 a.m. to 1,600 customers in parts Napa, Solano and Yolo counties. Just as that shutdown was called off, the utility warned 27,000 customers in Butte, Yuba, Nevada, El Dorado and Placer counties that their power would be cut from 9 p.m. through Sunday morning.

The end of the earlier shutdown was announced around 4 p.m., and the utility said power would be restored in those areas as soon as crews finished checking lines for any weather-related damage.

Conditions ripe for fire — winds, low humidity, dry vegetation and heat — were expected to last into Sunday. The National Weather Service office reported a 71 mph (114 kph) gust on one peak in the region.

A fire that erupted late in the day in Yolo County was estimated at 100 acres; firefighters halted the spread of another after 25 acres burned northeast of Calistoga in Napa County. The causes were not immediately known.

PG&E is under pressure to prevent fire starts after downed power lines and other company equipment have been blamed for conflagrations that began during so-called fire weather.

But there has been opposition from customers who rely on electrically powered life-support equipment as well as businesses that have had to shut down for lack of power.

“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 Friday.

California experienced a very wet winter and spring, and even vast areas that were scorched earth after last year’s wildfires now have new head-high brush that is rapidly browning as summer approaches.

Several fires have broken out.

More than 500 firefighters had been sent by Saturday night to fight the Sand Fire, which was first reported at 2:50 p.m., Cal Fire said. Saturday. No structures had burned as of 9 p.m. Saturday, but residents of Yolo County Road 41 north of Rumsey have been ordered to evacuate, Cal Fire said.

A grass fire Friday afternoon near the Solano County community of Fairfield forced people out of about 50 homes. But firefighters held it to 24 acres (10 hectares) without any structures lost and evacuations were lifted.

A wildfire near Interstate 5 in Stanislaus County grew to nearly 1 square mile (2.59 sq. kilometer). But it was 75 percent contained Saturday, according to the California Department of Forestry and Fire Protection.The state’s electricity providers have been given authority to shut off power when fire risk is extremely high. The California Public Utilities Commission has said they must do a better job of educating and notifying the public, as well as increase fire prevention efforts such as clearing brush and installing fire-resistant poles.

The National Weather Service’s red flag warning was issued for parts of the Central Valley and the Sacramento-San Joaquin River Delta for Saturday through Sunday at elevations below 1,000 feet (305 meters), where there has been less rain recently and the vegetation is driest.

A heat advisory issued for the region around the San Francisco Bay warned of record or near-record heat on Sunday, with widespread highs from 95 to 105 degrees (35 to 40.5 Celsius).