SAN FRANCISCO (CBS SF/AP) — Twin wildfires fueled by dry vegetation and hot, windy weather continued to grow Saturday in Mendocino and Lake counties, destroying 55 homes and forcing thousands of residents to flee their neighborhoods.

Flames engulf a ridge as the River Fire threatens the town of Lakeport, Calif. Aug. 3, 2018. (Getty Images)

California fire officials said Saturday that the Ranch and River fires of the Mendocino Complex, burning near Ukiah and Clear Lake, grew to almost a combined 250 square miles (201,000 acres). They have been burning since July 27. Their causes are under investigation.

The two fires cover an area larger than the Carr Fire that damaged parts of Redding last week.

As a precaution, new evacuations were called Friday. The fires are threatening about 9,000 homes.

The dual fires have charred an area of the forested, rural area five times the size of San Francisco and were only 34 percent contained Saturday.

The National Weather Service issued red flag warnings of critical fire weather conditions through Saturday night, saying a series of dry low-pressure systems passing through the region could bring wind gusts of up to 35 miles per hour that could turn small fires or even sparks into racing walls of flames.

Traffic passes through heavy smoke from the River Fire at sunset as it threatens the town of Lakeport, Calif. Aug. 3, 2018. (Getty Images)

“This is a particularly dangerous situation with extremely low humidity and high winds. New fires will grow rapidly out of control, in some cases people may not be able to evacuate safely in time should a fire approach,” the weather service said in its bulletin for the Mendocino area north of San Francisco.

Wind swept flames from the River Fire threatens the town of Lakeport, Calif. Aug. 3, 2018. (Getty Images)

The fires remained several miles from the evacuated communities along the eastern shore of Clear Lake but “it looks like there’s dicey weather on the way,” California Department of Forestry and Fire Protection spokeswoman Jane LaBoa said.

Meanwhile, some days-old evacuations were lifted Friday in an area near Redding, where armies of firefighters and fleets of aircraft have been battling the immense Carr Fire about 100 miles south of the Oregon line. Some areas on the fire’s southeastern flank were reopened to residents.

The Carr Fire was 41 percent contained Saturday after killing six people and incinerating 1,067 homes. California Department of Forestry and Fire Protection officials said it was caused by sparks from the steel wheel of a towed-trailer’s flat tire. It has burned 141,000 acres.

The fire burned slowly for days before winds suddenly whipped it up last week and drove it furiously through brush and timber.

The blaze burned so furiously on July 26 that it created a “fire whirl.” The twirling tower of flame reached speeds of 143 mph, which rivaled some of the most destructive Midwest tornados, National Weather Service meteorologist Duane Dykema said. The whirl uprooted trees and tore roofs from homes, Dykema said.

Gov. Jerry Brown Saturday inspected Redding neighborhoods wiped out by the Carr Fire and called on President Donald Trump to help California fight and recover from another devastating wildfire season.

The Democratic governor said he was confident the Republican president he has clashed with over immigration and pollution policies would send aid, which Trump did last year when the California’s wine country was hit hard.

“The president has been pretty good on helping us in disasters so I’m hopeful,” Brown said. “Tragedies bring people together.

Authorities said there are 17 major fires burning throughout California. In all, they have destroyed hundreds of homes and killed eight people.

In the Sierra Nevada, firefighters achieved 41 percent containment of the Ferguson Fire, a forest fire that has shut down Yosemite Valley and other adjacent portions of Yosemite National Park at what is normally the height of summer tourism.

The fire had reached into remote areas of the country’s third-oldest national park. Workers who live in Yosemite’s popular Valley region were ordered to leave Friday because of inaccessible roads.

The blaze has killed two firefighters.

A new report says the first firefighter, a California bulldozer operator, nearly slipped off a steep mountain trail three times before his vehicle finally rolled into a ravine and fatally crushed him.

Each earlier slip alone qualified as a “near miss” warning that the century-old mining trail could collapse, according to the Department of Forestry and Fire Protection’s preliminary report.

Braden Varney, 36, was working alone overnight July 14 fighting the wildfire while his assistant went to get a new hydraulic hose. Varney’s radio wasn’t communicating with headquarters, so his assistant relayed messages — until they lost contact.

The report says the death of the 10-year veteran highlights the need for better risk assessment, communication and supervision.

(© Copyright 2018 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)

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