The two Ranch and River fires, also known as the Mendocino Complex Fire, are the latest among a number of wildfires wreaking havoc in Southern California.
These two fires are burning about 100 miles (161 kilometres) north of San Francisco and are only 30 per cent contained as of Tuesday, fire officials said.
The blazes, which are burning just 14 miles apart, have so far burned 428 square miles (1,108 square kilometres).
At least 75 homes have been destroyed and more than 9,000 are being threatened.
The fire is now bigger than the Thomas Fire, which burned 281,893 acres in Santa Barbara and Ventura counties in 2017.
However, no deaths have been reported.
Almost 4,000 fires were burning across California on August 5, which has resulted in more than 600,000 acres being destroyed, according to Cal Fire.
This is more than double the number of acres burned this time last year, as well as four times the five-year average.
The fires are being blamed on scorching temperatures, but could be out by August 15.
However, they could get worse if the hot weather conditions persist.
Where is Ferguson fire?
The Ferguson fire, located in the Sierra National Forest and Stanislaus National Forest in California, has been burning for nearly three weeks.
The blaze has spread across 94, 331 acres and firefighters have so far contained 39 per cent,
Cal Fire said: “Over the past 48 hours, fire has impacted all of the roads used to access Yosemite Valley, burning dead and downed trees that can become very explosive and fall without warning.”
Where is Yosemite National Park?
The Ferguson fire has resulted in Yosemite National Park closing indefinitely.
The park is in California’s Sierra Nevada mountains.
Although Yosemite is not threatened by the fire, the decision to close was due to ensuring the safety of the many thousands of people who visit.