The Mendocino Complex fire is now the second-largest wildfire in California history, scorching more than 273,000 acres and frustrating firefighters as it continues to leap across natural and man-made barriers in Lake County, officials said Tuesday morning.

The Ranch and River fires, which make up the complex fire, had grown to 273,664 acres as of Monday morning, according to the California Department of Forestry and Fire Protection. The blaze was only 30% contained as of 7 a.m.

The blaze is on pace to become the largest wildfire in state history, surpassing the Thomas fire, which burned through more than 281,000 acres in Ventura and Santa Barbara counties late last year.

Officials said the Mendocino Complex fire has continued to grow by thousands of acres each day, even at night, when most fires normally calm down.

The fire has prompted evacuations in Mendocino, Lake and Colusa counties, but it has been less destructive to property than some of the other dozen-plus wildfires burning across the state because it continues to rage in remote areas.

But the fire’s sheer size and rate of spread is the latest signal of a remarkable fire year for California.

“It is extremely fast, extremely aggressive, extremely dangerous,” said Scott McLean, a deputy chief with the California Department of Forestry and Fire Protection. “Look how big it got, just in a matter of days. Look how fast this Mendocino Complex went up in ranking. That doesn’t happen. That just doesn’t happen.”

Years of drought have created ripe conditions for large-scale wildfires that spread rapidly. Of the five largest wildfires in state history, four have occurred since 2012.

There are 18 large wildfires burning across California now, scarring a combined 559,000 acres, officials have said. In Redding, the Carr fire has claimed seven lives and more than 1,000 homes while growing to 163,207 acres in size, making the deadly blaze now the 12th largest wildfire in state history, Cal Fire officials said in a statement.

Firefighters working overnight Sunday increased containment on the Carr fire to 45%, officials said during a Monday morning news briefing. The blaze chewed through about 3,000 more acres overnight as crews continued to build up containment lines, Cal Fire said.

Rescue crews there have been repeatedly hamstrung by intense heat and difficult terrain. The fire jumped the Sacramento River more than a week ago and raced into subdivisions in western Redding. Officials said Monday that shifting winds, steep canyons and rocky terrain on the fire’s northern edge along the Shasta and Trinity county border have made it difficult to attack the flames on the ground.

Bulldozers have scraped in defensive lines miles to the north and east, far from the fire’s edge. With Trinity Lake providing a natural barrier that has slowed the fire’s advance to the northwest, crews will spend the next several days tightening that perimeter until they find a position to make a final stand, officials said.

A high-pressure system moving into the area Monday could help with that effort, meteorologist Alex Hoon said during Monday’s briefing.

While that will create poor air quality for firefighters and virtually every community around the blaze, it also means the fire will be starved of the oxygen it needs to grow, he said.

“This is pretty much the best weather conditions we can ask for, for the beginning part of August. The fire’s not going to get up and move,” Hoon said.

The Carr fire has proved to be the deadliest in the state this year, claiming the lives of four residents, a Redding firefighter, a private bulldozer operator and a Pacific Gas & Electric utility worker.

Fire officials are also concerned about the growth of the Donnell fire, which has spread to 12,000 acres since it ignited last week in the Stanislaus National Forest. The fire began along the Stanislaus River and has triggered mandatory evacuations, but like several other blazes around the state, the fire is in steep terrain that has made containment efforts difficult, according to a news release issued by the U.S. Forest Service. The blaze was only at 1% containment as of Sunday night.

As the fires raged in Northern California, meteorologists issued red flag warnings in the Los Angeles area, where temperatures will reach the triple digits in several neighborhoods and cities early in the week.

Woodland Hills could see a high of 108, while Santa Clarita and Burbank could all see the mercury rise above 100 before Tuesday, according to the National Weather Service. Farther north, other cities that could experience 100-degree-plus heat are Ojai in Ventura County and Paso Robles in San Luis Obispo County.