A wildfire roaring through drought-parched Oregon is now so large it covers an area the size of Los Angeles and is generating its own weather.

The so-called Bootleg fire is the largest so far this year in the United States, having already burned more than 530 square miles of forest and grasslands and displaced more than 2,000 people.

The blaze, which has been burning for more than two weeks, has begun affecting winds and disrupting the surrounding atmosphere.

“The fire is so large and generating so much energy and extreme heat that it’s changing the weather,” said Marcus Kauffman, a spokesman for the state forestry department. “Normally the weather predicts what the fire will do. In this case, the fire is predicting what the weather will do.”

Experts say the blaze is cresting Pyrocumulus clouds, which form when extreme heat from the flames of a wildfire force the air to rapidly rise, condensing and cooling any moisture on smoke particles produced by the fire. These clouds essentially become their own thunderstorms and can contain lightning and strong winds.

The devastating Bootleg Fire burns through the night in southern Oregon

US Bootleg Fires Oregon

"We are fighting the fire aggressively, and there are active efforts to build a containment line, both direct and indirect, wherever it is safe to do so," Mr Kauffman said.

But the amount of landscape charred since the blaze erupted on July 6 grew another 40,000 acres on Monday alone to reach an estimated total of almost 340,000 acres – more than half the land mass of Rhode Island, the US Forest Service reported.

Only three other Oregon wildfires over the past century have consumed more acreage, according to state forestry figures.

At last report, the fire had destroyed 67 homes and was threatening 2,460 more. More than 100 outbuildings and other structures have also been lost. An estimated 2,100 people were under evacuation orders on Monday and many more were on standby to be ready to flee at a moment’s notice.

Nicolas Bey, 11, hugs his father, Sayyid Bey, after their home was destroyed

The Bootleg stood as the biggest, by far, of 80 major active wildfires that have collectively burned nearly 1.2 million acres in 13 states, according to the National Interagency Fire Center in Boise, Idaho. More than 19,600 firefighters and support personnel are confronting those flames.

The spate of conflagrations, marking a heavier-than-normal start of the Western wildfire season, has coincided with record-shattering heat that has baked much of the region in recent weeks and is blamed for hundreds of deaths.

Scientists have said the growing frequency and intensity of wildfires are largely attributable to prolonged drought and increasing bouts of excessive heat that are symptomatic of climate change.

Water-dropping helicopters and aeroplane tankers have helped tackle the flames

The remnants of cars destroyed by the Bootleg Fire are seen in a small community near Beatty

Since starting nearly two weeks ago, the Bootleg fire has thrived from a combustible triad of weather conditions – gusty winds, high temperatures and low humidity – that are expected to persist in the days ahead. Forecasts on Monday added a chance of thunderstorms to the mix.

"Thunderstorms often just come with dry lightning and wind and don’t necessarily produce any precipitation," Mr Kauffman said.

The cause of the Bootleg was under investigation.

Scientists say the growing frequency and intensity of wildfires are largely attributable to climate change

The destructive Bootleg Fire, one of the largest in modern Oregon history

The Bootleg Fire is the third-largest wildfire in the state’s history, Mr Kauffman said. The Long Draw Fire in 2012 burned 557,028 acres and is the largest wildfire in Oregon since 1900. The Biscuit Fire in 2002 became the state’s second-largest fire, burning nearly 500,000 acres.