The Wragg fire has thus far consumed over 6,000 acres

The Rocky fire has forced the evacuation of several thousand people. Josh Edelson / AFP / Getty Images

The fire has led to the closing of several highways and destroyed two dozen homes. Justin Sullivan / Getty Images

The Rocky fire has proved exceptionally difficult to contain because weather conditions have made its movements unpredictable. Justin Sullivan / Getty Images

Over 1,900 firefighters have been dispatched to fight the Rocky fire, part of a force of 9,000 firefighters working across the state. Loren Elliott / San Francisco Chronicle / Polaris

Firefighters watch a plumes of smoke from the Rocky fire, Aug. 1, 2015 near Clearlake, California. The blaze is the fiercest of 20 fires burning in Northern California. Justin Sullivan / Getty Images

A wildfire raging through the foothills and canyons of Northern California's coastal mountains roared into its sixth day on Monday, leaving at least two dozen homes in ruins and displacing thousands of residents after the fire more that doubled in size on Sunday.

The blaze, which has scorched about 93 square miles east of Lower Lake, a town about 110 miles north of San Francisco, was the fiercest of 20 large fires being battled by 9,000 firefighters across the state, officials said.

Capt. Don Camp of California's Department of Forestry and Fire Protection said containment of the fire in the Lower Lake area was at 12 percent Monday morning after being stuck at 5 percent for days.

"This is a very fast-moving wildfire," said Daniel Berlant, a spokesman for the California Department of Forestry and Fire Prevention, or Cal Fire, on Sunday.

A separate blaze that killed a U.S. forest ranger on Thursday near the Oregon border has also expanded, but remains a fraction of the size of the Rocky fire, which erupted in Lake County on Wednesday and has proved the most destructive.

Cal Fire officials “are calling the behavior of this fire unprecedented,” Jason Shanley, a spokesman for the California Department of Forestry and Fire Protection, told the Sacramento Bee. “It is jaw-dropping to see some of the things it is doing" in wind that is causing flames “to go in all different directions.”

Some 20,000 acres of scrub oak and brush ravaged by the Rocky fire over a five-hour period on Saturday night represented "unprecedented growth in that short amount of time," Berlant said. By Sunday evening, the blaze had blackened another 7,000 acres along the rugged eastern flanks of California's Northern Coast Ranges, officials said.

But in a small sign of optimism on Monday morning, firefighters were aided by lower temperatures and higher humidity, which allowed for the slight increase in the fire's containment.

The Rocky fire has closed parts of Highway 20 and Highway 16, destroyed at least 24 homes and 26 more outbuildings, and threatened an additional 6,301 structures as of Sunday, according to Cal Fire.

"The biggest challenge is the extreme and explosive rates of spread of these fires," said California's Forestry and Fire Protection Director Ken Pimlott.

Cal Fire reported that 1,942 personnel are fighting the blaze, with 37 water tenders, 19 helicopters, 56 bulldozers and 37 hand crews. The California and Colorado national guards deployed four C-130 air tankers to the remote area and the first is only 5 percent contained, the same percentage as Saturday, according to the website. About 12,000 people have been evacuated or are under evacuation advisories.

Brad Alexander, chief spokesman for the Gov. Jerry Brown's emergency services office told the Los Angeles Times that the fire is in "an area that hasn't had burning in several decades.

"They've got chaparral that is over 6 feet tall," Alexander said. "When you have vegetation that big and dense in an area like that it is going to cause flames to race up and down canyon walls and hillsides.

Drought-stricken brush and grasslands have made parts of California vulnerable to wildfires.

In Humboldt County, 600 firefighters were battling 18 small blazes Sunday that were sparked by lightning. At least 70 fires have been reported in the area since Thursday. Of those, 52 have been contained, Cal Fire said. The blazes have charred 2,000 acres and destroyed two structures in steep, difficult to access terrain.

In the Shasta-Trinity National Forest, there are 40 fires covering 23,729 acres in the so-called Fork Complex Fire in Trinity County, according to Cal Fire.

Among numerous fires burning in the state is the Frog Fire, which officials said killed a firefighter on Thursday. David Ruhl, 38, a married father of two from Rapid City, South Dakota, died while assigned to the fire in the Modoc National Forest, 100 miles south of California's border with Oregon.

Ruhl was alone and working as incident commander on the fire, said Modoc National Forest spokesman Ken Sandusky. It is common for a leader on a fire to travel alone, Sandusky said, but he declined to release more details on the death.

The Frog Fire is about 5 percent contained, has grown to 3,900 acres and erratic winds have pushed it in all directions, according to the U.S. Forest Service's InciWeb online fire information center.

A red-flag warning, designating the threat of gusty winds that risk fanning flames, was expected to remain in effect until late Sunday in the area of the Frog Fire. InciWeb said the flames are not expected to be fully under control until Aug. 12.

Three firefighters who were burned on a fire northeast of Sacramento on Saturday have been released from the hospital. One has returned to duty and all are expected to make a full recovery, fire officials said.

A fourth firefighter remains hospitalized with serious burns.

Al Jazeera and wire services