11 a.m.

A compost pile at Green Works on Eagle Ridge Drive caught fire Wednesday morning.

Firefighters were on the scene and will spend the next few hours putting it out.

The smoke in Tuolumne County Wednesday is from the Briceberg Fire burning near Yosemite. In Calaveras County, smoke was from a planned burn in the Humboldt–Toiyabe National Forest.

10 a.m.

Tuolumne County emergency operations announced this morning that PG&E will begin shutting off power to all customers in the county at noon and the process could take until 1 p.m.

Calaveras County officials said the shut down could occur between noon and 2 p.m.

They said there was a small portion of Calaveras County that had been shut down already but they did not know the extent because they could not get access to the PG&E website.

People across northern California were experiencing the same, resulting in an increasing level of frustration with the giant utility.

Summerville High Principal Kellene Ditler said her staff had worked for two days on an emergency plan to meet all contingencies, including no power and power going off during the school day. As with all public schools, Summerville was in session and would finish the day at 2:05 p.m., a previously scheduled early release day.

Tuolumne County School Superintendent Cathy Parker told all schools to cancel if the power was out before the start of the school day.

Ditler said some teachers came to school with battery-powered lamps in case the power went off during the school day. Most classrooms have good natural light. Teachers prepared lessons that didn't require technology.

"We have a super flexible staff," she said.

If the power is off on Thursday, school will be cancelled but all administrators will be on campus and security personnel will be on site through the outage.

Cell phone problems Tuesday night were likely the result of a collision and not related to PG&E, a spokesman for AT&T said.

9:55 a.m. report from AP

Pacific Gas and Electric shut off power to more than half a million customers Wednesday in Northern California in the biggest planned shut off in the state's history.

Southern California Edison is considering power shutoffs to nearly 174,000 customers in nine counties and San Diego Gas & Electric says it has notified about 30,000 customers in backcountry areas.

Red Flag warnings for critical fire weather are expected to go into effect Thursday because of forecasts calling for Southern California's notoriously gusty Santa Ana winds.

9:05 a.m. report from AP

Residents in Sonoma are swarming to the few businesses open in the town's square amid a power outage expected to last for days — a bakery with lines out the door and a bar lit with lanterns.

At the Basque Boulangerie Cafe, workers used battery-powered lights and kept track of cash-only sales by listing them on a sheet of paper. John Vitale says he was happy to find out the cafe had opened after employees prepared the outage by baking bread and pastries.

Vitale tells KTVU-TV he drove around Sonoma looking for a place to get breakfast and feels fortunate to have found coffee and pastries.

7:39 a.m. report from AP

The California Transportation Department says two tunnels in the San Francisco Bay Area that depend on electricity to function will remain open during a power outage affecting a large swath of Northern California.

Caltrans crews worked through the night to install generators at the Caldecott Tunnel linking the East Bay to San Francisco and the Tom Lantos Tunnel on State Route 1 in Pacifica.

The agency says the generators should be working by midday Wednesday when Pacific Gas and Electric is expected to shut off power in the Bay Area.