SOUTH LAKE TAHOE (AP/CBS13) – A huge firefighting force gathered Tuesday to defend Lake Tahoe from a raging wildfire that forced the evacuation of California communities on the south end of the alpine resort and put others across the state line in Nevada on notice to be ready to flee.

The streets of the popular vacation hot spot, normally filled with thousands of summer tourists, were all but deserted after rapid growth of the Caldor Fire forced a mass evacuation of South Lake Tahoe on Monday and triggered hours of gridlocked traffic.

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“It’s more out of control than I thought,” evacuee Glen Naasz said of the fire that by late Monday had been pushed by strong winds across two major highways, burning mountain cabins as it swept down slopes into the Tahoe Basin.

More firefighters arrived just after dark Monday, and many were dispatched to protect homes in the Christmas Valley area, about 10 miles (16 kilometers) from the city of South Lake Tahoe.

Thick smoke prevented air firefighting operations periodically last week. But since then, 23 helicopters and three air tankers dumped thousands of gallons of water and retardant on the fire, fire spokesman Dominic Polito said.

The National Weather Service warned of critical fire weather conditions through Wednesday due to strong gusts, very low humidity and extremely dry fuel.

As flames advanced toward South Lake Tahoe, residents just over the state line in Nevada faced evacuation warnings. Nevada Gov. Steve Sisolak on Monday declared a state of emergency, citing the high risk that the California fire would burn into his state.

Casino regulators were monitoring operations at the four largest gambling properties in Stateline, the Nevada town adjacent to South Lake Tahoe, said Kelly Colvin, audit chief for the Nevada Gaming Control Board.

Gambling has been significantly curtailed as staffing is limited due to mandatory evacuations in California, board analyst and spokesman Michael Lawton said.

Hotels are housing evacuees and fire crews. In all, Harrah’s, Harveys Lake Tahoe Casino, the Hard Rock and Montbleu Resort have more than 2,200 hotel rooms.

Evacuation shelters at community centers in Carson City and Douglas County were at capacity, officials said Tuesday. Additional sites were open at a park in Carson City, the Reno Sparks Convention Center and a rodeo event center in Dayton and Lyon County fairgrounds in Yerington.

“There is fire activity happening in California that we have never seen before. The critical thing for the public to know is evacuate early,” said Chief Thom Porter, director of the California Department of Forestry and Fire Protection, or Cal Fire. “For the rest of you in California: Every acre can, and will, burn someday in this state.”

The threat of fire is so widespread that the U.S. Forest Service announced Monday that all national forests in California would be closed until Sept. 17.

“We do not take this decision lightly, but this is the best choice for public safety,” Regional Forester Jennifer Eberlien said.

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More than 15,000 firefighters were battling dozens of California blazes, including crews from Utah, Washington, Wisconsin and West Virginia, said Mark Ghilarducci, director of California’s Office of Emergency Services. Crews from Louisiana had to return to that state because of Hurricane Ida, he said.

Only twice in California history have blazes burned from one side of the Sierra Nevada to the other, both this month, with the Caldor and Dixie fires, Porter said.

The Dixie, the second-largest wildfire in state history at 1,215 square miles (3,147 square kilometers), was burning about 65 miles (105 kilometers) north of the Lake Tahoe-area blaze. It prompted new evacuation orders and warnings Monday.

The Lake Tahoe area is usually a year-round recreational paradise offering beaches, water sports, hiking, ski resorts and golfing. South Lake Tahoe bustles with outdoor activities.

The last two wildfires that ripped through populated areas near Tahoe were the Angora Fire that destroyed more than 200 homes in 2007 and the Gondola Fire in 2002 that ignited near a chairlift at Heavenly Mountain Resort.

Since then, dead trees have accumulated and the region has coped with serious droughts, Wallace said. Climate change has made the West much warmer and drier in the past 30 years and will continue to make weather more extreme and wildfires more frequent and destructive, scientists say.

The California Highway Patrol added officers to help guide chaotic traffic out of South Lake Tahoe, which has one main artery. Traffic crawled at times Monday, but Highway 50 had cleared by afternoon.

Just a tiny fraction of city residents – 20 people – refused to evacuate, said Lindsey Baker, South Lake Tahoe spokeswoman. She said the gridlock indicated that people were obeying orders to flee.

The Caldor Fire has scorched nearly 300 square miles (777 square kilometers) since breaking out Aug. 14. After the weekend’s fierce burning, containment dropped from 19% to 16%.

More than 600 structures have been destroyed, and at least 33,000 more were threatened.

Diane Kinney, who has lived in South Lake Tahoe since the 1970s, said it was the first time her neighborhood had been ordered to evacuate. She and her husband packed up keepsakes, jewelry and insurance papers shortly after noon. They left behind their 1964 Chevrolet Chevelle.

“There are definitely advantages of being in the mountains, being with these beautiful pine trees,” she said. “But we definitely have to get out now.”

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Copyright 2021 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.