Lane Lawder tries to save his home near Clearlake Oaks, California, on August 4, 2018

Multiple wildfires that together grew Monday to nearly the size of Los Angeles could become the worst in fire-prone California's history, authorities warned.

The River and Ranch fires, which together are called the Mendocino Complex, blackened an area of 273,660 acres (110,750 hectares).

Authorities from state agency CalFire reported before midday that it already had mushroomed into the second worst blaze in state history in terms of area burned.

"I expect to see it to be number one, unfortunately, this evening," CalFire spokesman Scott McLean said on Facebook.

The largest ever until Monday had been the Thomas Fire in December 2017. It was 440 square miles (1,140 square kilometers)—almost the size of Los Angeles.

Further north in the state, the Carr Fire has scorched 154,524 acres of land since July 23, when authorities say it was triggered by the "mechanical failure of a vehicle" that caused sparks to fly in tinderbox-dry conditions.

The fire has razed more than 1,600 buildings, including some 1,000 homes, state officials say.

More than 14,000 firefighters were battling the blazes across the state, which has lost another 918 square miles already this year.

The wildfires are "extremely fast, extremely aggressive, extremely dangerous," said Scott McLean, a deputy chief with the California Department of Forestry and Fire Protection.

An air tanker drops retardant on the Ranch Fire, part of the Mendocino Complex

"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."

President Donald Trump raised eyebrows by tweeting about the wildfires inaccurately, claiming there was not enough to fight them.

"California wildfires are being magnified & made so much worse by the bad environmental laws which aren't allowing massive amounts of readily available water to be properly utilized," Trump said.

"It is being diverted into the Pacific Ocean. Must also tree clear to stop fire from spreading!"

In fact, "we have plenty of water to fight these wildfires, but let's be clear: It's our changing climate that is leading to more severe and destructive fires," Daniel Berlant, CalFire assistant deputy director, told The New York Times.

In an unrelated long-running dispute, farmers have demanded more water to irrigate crops for years, while environmentalists say diverting more water to crops would kill off fish stock and hurt rivers.