Wildfires have burned a record two million acres in California this year, and the danger for more destruction is so high the U.S. Forest Service announced Monday it was closing all eight national forests in the southern half of the state.

After a typically dry summer, California is parched heading into fall and what normally is the most dangerous time for wildfires. Two of the three largest fires in state history are burning in the San Francisco Bay Area. More than 14,000 firefighters are battling those fires and dozens of others around California.

A three-day heat wave raged through much of the state during Labor Day weekend. But right behind it was a weather system with dry winds that could fan fires. The state's largest utility, Pacific Gas & Electric, was preparing to cut power to 158,000 customers in 21 counties in the northern half of the state to reduce the possibility its lines and other equipment could spark new fires.

Randy Moore, regional forester for the Forest Service's Pacific Southwest Region that covers California, announced the national forest closures and said the decision would be re-evaluated daily. Campgrounds at all national forests in the state were closed.

"The wildfire situation throughout California is dangerous and must be taken seriously." Moore said. "Existing fires are displaying extreme fire behavior, new fire starts are likely, weather conditions are worsening, and we simply do not have enough resources to fully fight and contain every fire."

Lynne Tolmachoff, spokeswoman for the California Department of Forestry and Fire Protection, or Cal Fire, said it's "unnerving" to have reached a record for acreage burned when September and October usually are the worst for fires because vegetation has dried out and high winds are more common. The previous high was 1.96 million acres burned in 2018. Cal Fire began tracking the numbers in 1987.

"We started getting information about how many people were out there, how many people to expect, and that number kept growing. So we knew that it was a dire situation," Rosamond said.

Rosamond called the conditions "extreme" and said it was one of the most difficult flying missions in his 25 years as a military pilot.

Record-breaking temperatures were driving the highest power use of the year, and transmission losses because of wildfires have cut into supplies. Throughout the holiday weekend, the California Independent System Operator that manages the state's power grid warned of outages if residents didn't reduce their electricity usage. But none had occurred by late Monday afternoon.

Pacific Gas & Electric (PG&E) warned it might cut power starting late Monday because of the increased fire danger. It expects to cut power to more than 500,000 people this week to prevent live wires from sparking wildfires.

PG&E received criticism for its handling of planned power outages last year. It shut off power for 940,000 homes and businesses in Northern California, leaving as many as 2.7 million people without electricity last year.

The utility company said it has learned from past problems, "and this year will be making events smaller in size, shorter in length and smarter for customers." 

California has seen 900 wildfires since August 15, many of them started by an intense series of thousands of lightning strikes in mid-August. There have been eight fire deaths and more than 3,300 structures destroyed.

(With input from AP)