SAN FRANCISCO — The unprecedented number and size of wildfires burning in California this year has forced firefighters to strategically choose which ones to tackle.

Their plan is this: Crews are dispatched to protect communities in the path of flames, while blazes are allowed to chew through acres of forest land.

Officials say the tactic is necessary in a fire season that already has seen hot weather, rough terrain and lightning storms complicate efforts to bring blazes under control.

“It’s like eating an elephant — you’ve got to eat it one bite at a time,” said Jason Kirchner, a spokesman for the U.S. Forest Service. “We have to take a step back, figure out where the best place is to make a stand and sometimes wait for the fire to come to us in those situations.”

Long-running wildfires are not unusual in California. It was four months before firefighters controlled a blaze that blackened more than 375 square miles of Santa Barbara County backcountry last year.

What is extraordinary this year is the number of fires burning at the same time, Kirchner said. The weekend of June 21 saw some 1,200 fires burning — a figure Forest Service officials said appeared to be an all-time record in California.

The Forest Service put the figure at about 600 on Monday. It attributed the gains to its tactic of attacking small fires first, and to significant assistance from other states and from Canada.

State officials, however, counted more than 1,000 ongoing blazes. The source of the discrepancy apparently was a different counting method.

Also unusual, Kirchner said, was that there have been no significant injuries to civilians or firefighters even though some 570 square miles have burned in California this season. There were a few minor injuries as harsh terrain hampered firefighters’ efforts to battle a blaze in the Shasta-Trinity National Forest.

“It is extremely steep, very rugged territory, and there are a lot of injuries, twisting ankles, slipping on hills,” Kirchner said. Burning debris is “rolling downhill right past your containment line. It’s very complicated, difficult, dirty firefighting work.”

Even so, firefighters managed to increase their containment of that 55-square-mile fire to 36 percent by Monday evening. A smaller blaze in the nearby Trinity Alps Wilderness, a popular summer hiking spot, was only 2 percent contained after scorching more than 4 square acres.

Two wildfires choked parts of the Sierra Nevada foothills, sending up plumes of smoke that darkened patches of the 100-mile stretch between Sacramento and Reno.

The fires in the Tahoe National Forest blanketed portions of the Interstate 80 corridor linking the two cities and the foothill communities in between where tens of thousands of people live.

Along the Pacific, fire officials said fog and humidity helped them gain ground on a blaze in the Los Padres National Forest that was just 3 percent contained and had blackened nearly 62 square miles near the storied town of Big Sur.

Firefighters poured personnel and equipment into the area to ensure the fire did not reach the town, said John Ahlman, a Los Padres forest spokesman.

Officials said there was a possibility of rain in the far northern part of the state this week. But the changing weather pattern also could bring new lightning and high winds, which could touch off new blazes and fan the current ones, said John Heil, a Forest Service spokesman.

Even a modest rain storm — highly unusual in July — would do little to diminish the likelihood of a long, tough fire season, Heil said.

“Unless it rains, and we get some really good rainfall, you can pretty much expect it to be here right through October,” he said.

Meanwhile, a wildfire that forced the evacuation of dozens of residents in a northern Arizona community crept to within 500 feet of some homes Monday but firefighters managed to keep it from moving closer, a spokeswoman said.

The wildfire had charred about 5,300 acres — or more than 2 square miles — near the community of Crown King as of late Monday. Three homes and four other structures had been destroyed, Debbie Maneely, a spokeswoman for the Prescott National Forest.

“It’s still a touch-and-go situation in there,” Maneely said.