(CNN)A major California utility has temporarily turned off power for almost 60,000 customers because of fire threats.
Pacific Gas & Electric, based in San Francisco, announced the move because of elevated risks of fire weather -- a combination of strong winds, low humidity and dry conditions on the ground. The initiative is designed to prevent power lines from sparking fires.
The National Weather Service said a Red Flag Warning -- an alert that signals the potential of dire fire threat conditions -- continues through Monday morning for higher elevations of the North Bay and East Bay in northern California.
More than 22 million people are under Red Flag Warnings both in northern and southern California, CNN meteorologist Haley Brink said. An elevated risk of fire weather is forecast for northern areas and an extreme risk of fire weather has been posted for southern areas, including parts of Los Angeles and Ventura counties.
Sustained winds of 30 to 40 mph are possible Monday. Humidity below 15% is forecast, and wind gusts up to 70 mph are possible in the higher elevations, canyons and passes, Brink said.
"It's fire weather season," Brink said. "Any new fires that do form today will spread rapidly."
PG&E on Sunday night announced the shutting off of power in extreme fire-risk areas, citing local weather forecasts calling for wind gusts up to 50 mph.
The utility shut off power in parts of El Dorado, Amador and Calaveras counties in the Sierra Foothills, affecting about 42,000 customers, and in parts of Lake, Napa and Sonoma counties in the North Bay affecting 17,483 customers. The company said it had planned to turn off power in other parts of the Sierra Foothills.
PG&E said it is working with first responders and state and local agencies on the fire threats.
The utility provides natural gas and electric service to approximately 16 million people over 70,000 square mles in northern and central California.
"Nothing is more important than the safety of our customers and the communities we serve," said Pat Hogan, senior vice president of electric operations.
"We know how much our customers rely on electric service, and we have made the decision to turn off power as a last resort given the extreme fire danger conditions these communities are experiencing. PG&E has a plan. We want our customers to have plans, too," he said.
PG&E said its crews will inspect lines for repairs and safely bring back power after "extreme weather has passed, and conditions are safe."
"Most customers are expected to be restored by Monday night (October 15), with some outages potentially lasting into Tuesday," the utility said.
Other California utilities are gearing up to deal with the fire threats, including turning off power.
San Diego Gas & Electric also said it has plans to notify customers who live in "high-wind, high fire zones about the potential for public safety power shutoffs due to weather and fire conditions."