Power was shut off to about 118,500 customers in parts of more than a dozen Northern California counties late Sunday in an unprecedented move to pre-empt wildfires with strong winds and extreme weather conditions.

Utility company Pacific Gas and Electric, or PG&E, said it was shutting off power to help reduce the risk of wildfires. Some of the deadly infernos that engulfed the state this time last year were caused by downed power lines and damaged electrical equipment.

The National Weather Service warned Sunday of critical fire-related weather conditions in the North Bay Mountains and East Bay Hills continuing through Monday morning due to a combination of strong, gusty offshore winds and low relative humidity.

Flowers mark the spot where Mike Rippey's family died in the Atlas Fire just after it began, on Oct. 12, 2017, near Napa, California. David McNew / Getty Images

Red flag fire warnings hit several areas, including the hills of Napa and eastern Sonoma counties, the Diablo Range, the Sacramento Valley, and the northern Sierra Nevada and Northern Coast Range.

PG&E and county officials were contacting customers directly and providing early warning notification, when and where possible, via automated calls, texts and emails, reported NBC Bay Area.

The utility went ahead with the shutoff plan in some extreme fire-risk areas in the northern part of the state and near the Sierra Nevada as early as Sunday afternoon and then expanded it down to some areas of the North Bay, according to the station.

The utility said most customers can expect power to be restored on Monday night, with some outages potentially lasting into Tuesday.

Some school districts in Napa and Lake counties have canceled classes Monday because of the power shutoff.

"We know how much our customers rely on electric service and would only consider temporarily turning off power in the interest of safety, and as a last resort during extreme weather conditions," said Pat Hogan, senior vice president of electric operations.

In June, California Department of Forestry and Fire Protection, or Cal Fire, announced that the utility's "electric power and distribution lines, conductors and the failure of power poles" caused at least a dozen wildfires in six Northern California counties a year ago during the state's deadliest and costliest wildfire season. A total of 44 people died and more than 6,000 homes were destroyed by blazes that devastated much of Sonoma County and elsewhere in the region.

The so-called October 2017 Fire Siege involved more than 170 fires and burned at least 245,000 acres in Northern California. About 11,000 firefighters from 17 states and Australia helped battle the blazes.

PG&E has faced a growing financial liability over wildfires in the state. The utility has told shareholders it expects to pay more than $2.5 billion in damages. California law compels utilities to pay for damages from wildfires if their equipment caused the blazes — even if the utilities weren't negligent.