There’s growing hope the Caldor fire won’t reach Lake Tahoe.

As of Thursday evening, the Caldor fire had burned more than 210,000 acres and was 27 percent contained. Crews continued dropping hundreds of thousands of gallons of water and fire retardant while firefighters crossed the water by boat — pumping water from Lake Tahoe to save remote cabins and vacation homes.

Jeffrey Spencer, 61, who evacuated with his wife and mother-in-law from their home near the Eldorado National Forest, about 10 miles south of Lake Tahoe, said that though the fire continued to burn just miles from their house, he was feeling “cautiously hopeful.”

“Our lives and important papers and valuables, we got to get out,” Mr. Spencer said. “The rest can be replaced.”

The city would give priority to older people and disabled residents and would then make the option available to the general public, he said.

Mayor LaToya Cantrell noted that in addition to electricity, access to fuel continued to be a challenge for city residents. “We just have not received adequate fueling sources to the general public,” she said.

In Broussard, horns honked louder and louder in a long line at a gas station where Pat Hille and Robin Corrabi filled up brand-new gas cans, their compact S.U.V. packed with supplies to take back to Ms. Hille’s family in LaPlace.

“If we get water back, it would make a difference,” Ms. Corrabi said.

The deaths of the nursing home residents in Tangipahoa Parish, north of New Orleans, raised the death toll of the storm and its aftermath in the Southeast to at least 16, from causes including carbon monoxide poisoning and electrocution.

“It’s very disheartening,” said Robby Miller, the Tangipahoa Parish president.

The mounting toll came as hundreds of thousands of residents of Louisiana and Mississippi spent a fourth day cleaning up the storm’s debris in darkness, amid soaring temperatures, and without easy access to the basic necessities: fresh water and meals.

By Thursday, electricity had been restored to customers in areas including Baton Rouge and St. Bernard and St. Jefferson Parishes, officials said. But in and around New Orleans, many people remained without power. Patience was waning.

Officials in New Orleans announced on Thursday that they were organizing a voluntary evacuation option for residents hoping to get out of the city. Details of that plan are still in the works, but it would allow residents to be taken to a state-run shelter outside the city, said Collin Arnold, the New Orleans director of homeland security.

The city would give priority to older people and disabled residents and would then make the option available to the general public, he said.

Across Louisiana, there were still hundreds of thousands of customers without power on Thursday, including nearly 600,000 served by Entergy. By early afternoon, 30,000 power customers in New Orleans had their electricity restored, said Ramsey Green, the city’s deputy chief administrative officer for infrastructure.

Mayor LaToya Cantrell, speaking at an afternoon briefing, noted that in addition to electricity, access to fuel continued to be a challenge for city residents. “We just have not received adequate fueling sources to the general public,” Ms. Cantrell said, adding that “when we get more, we shall share more.”

In Broussard, horns honked louder and louder in a long line at a gas station where Pat Hille and Robin Corrabi filled up brand-new gas cans, their compact S.U.V. packed with supplies to take back to Ms. Hille’s family in LaPlace.

“If we get water back, it would make a difference,” Ms. Corrabi said.

President Biden, who is expected to visit the state on Friday, said the flash floods that had inundated New York City and the powerful winds that had knocked out power in Louisiana were a sign that “extreme storms and the climate crisis are here” and that the storms and fires creating life-or-death situations across the country constituted “one of the great challenges of our time.”

Local officials offered upbeat assessments.

“I think the key in what we are trying to do is offer some progress, and that is the goal,” Mr. Arnold, the homeland security director in New Orleans, said. “Every day, we open a new site, some new service.”

He added that “there are lots of lessons from this, after all of this is done.”

Southeast of Susanville, some residents and firefighters in Milford have been clearing vegetation around homes and properties — the town of about 200 people is among the most likely to be affected by the fire next, authorities said.

“The fire is not over the mountain yet but you never know,” said David Hammond, 23, whose parents run a convenience store near Milford that staff members said was among the only places in the region where residents could still buy food and gas.

Mr. Hammond’s family had been wetting down its house with timed sprinklers, and had passports, clothing and other important belongings packed into cars, he added, “in case we’ve got to go.”

In other parts of the Sierra Nevada, crews are stamping out the aftermath of the fire’s wrath in challenging terrain.

More than 4,000 firefighters continue to battle the fire, though last month, several were diverted to the Caldor fire, which is also burning in the Sierra Nevada and now threatening communities on Lake Tahoe.

Several towns in the path of the Dixie fire are still under evacuation warnings and orders, and close to 3,900 people remain evacuated from their homes, said Brian Scott, a spokesman with the incident management team on the fire.

“We would hope that we’re on the downhill slide,” Mr. Scott, who is currently based in Quincy, said of the fire. “But after seeing what Mother Nature can do with the winds, and the severe dryness of the fuels,” he added, “it’s just hard to venture a guess.”

The family did not survive.

Darlene Lee, 48, was in a basement apartment that belonged to the super of a condominium in Central Parkway, Queens. Flooding burst through a glass sliding door in the apartment, and quickly filled it with about six feet of murky water.

The water pinned Ms. Lee between the apartment’s steel front door and the door frame, leaving her wedged and unable to escape.

Patricia Fuentes, the property manager, had just gotten off work when she heard Ms. Lee screaming for help and found her stuck. Ms. Fuentes ran to the lobby to call for aid, and Jayson Jordan, the assistant super, and Andy Tapia, a handyman, jumped through the broken glass door to get to Ms. Lee.

But they could not save her. Ms. Lee was pinned and Mr. Tapia tried to help her keep her above the chin-deep water. Eventually, the men were able to pry her from the door, but it was too late, Mr. Jordan said. Ms. Lee was killed by the storm.

In Cypress Hills, Brooklyn, Ricardo Garcia was awakened by a surge of water that he said exploded through the door of his shared basement apartment at about 10:15 p.m. In moments, it was up to his knees, then his waist, then his chest.

Mr. Garcia, 50, banged on the door next to his, waking another roommate, Oliver De La Cruz, who was shaking on Thursday morning as he looked at the water stains that reached to the ceiling of his ruined room.

“I almost died inside here, I almost died, man,” said Mr. De La Cruz, 22.

Mr. De La Cruz broke down his bedroom door to escape in his boxer shorts. Mr. Garcia said that he and Mr. De La Cruz climbed to the first floor, struggling against the water pouring down the stairs.

Mr. De La Cruz found his upstairs neighbor, Roxanna Florentino, who has lived in the building for 18 years. She said she heard another man, 66-year-old Roberto Bravo, crying out for help from a back bedroom in the basement apartment.

Ms. Florentino said Mr. Bravo was pleading for help in Spanish, and neighbors were trying to reach him. But water was pouring through both the front door and a window. She realized Mr. Bravo’s screaming had stopped.

On Thursday, it was clear that the water had risen so forcefully where Mr. Bravo had been that it tore off the door and broke though the ceiling, leaving dank decay. The Ecuadorean flag hanging on his wall was soaked and muddied, the floor below strewn with debris, along with a water-stained photo of Mr. Bravo in a tuxedo at a formal event.

Ms. Florentino made her first of four 911 calls at 10:15 p.m. Firefighters arrived an hour later. They brought out Mr. Bravo’s body.

She tried to sleep but each time she drifted off, she heard Mr. Bravo’s voice, calling a last time.

“It’s so hard when someone asks for help and you can’t help them,” she said.

The damage was all the more harrowing given that it came with relatively little warning from political leaders who were already contending with a pandemic that continues to kill thousands of Americans each week.

Those leaders, from President Biden down to New York’s Democratic nominee for mayor, Eric Adams, expressed a similar sentiment in their reactions to the storm: Climate change is here.

In a speech from the White House, Mr. Biden called the storm “devastating” before pivoting to discussion of the other natural disasters afflicting the United States, including wildfires in the West and the damage inflicted by Hurricane Ida in the South.

“This destruction is everywhere,” he said. “It’s a matter of life and death and we’re all in this together. This is one of the great challenges of our time.”

Gov. Kathy C. Hochul of New York, who assumed office a little more than a week before the storm hit, offered a similar message.

“It is not a future threat,” she said of climate change. “It is a current threat.”

And Mr. Adams, who is likely to become New York City’s next mayor, mixed his acknowledgment of the threat of the climate crisis with a sentiment that many New Yorkers shared, days after the rain stopped.

“I have never witnessed something like this,” he said.

That means when a rainstorm does eventually form, there is more water that can fall to the ground, sometimes within a very short period. Recent studies have detected an increase in hourly rainfall extremes in parts of the United States, Europe, Australia and Asia.

And if the planet keeps getting hotter, the threat of more intense rainfall will grow. Earth has already warmed roughly 1.1 degrees Celsius since preindustrial times, driven by greenhouse gas emissions from the burning of fossil fuels and deforestation. Without swift action to reduce those emissions, a recent report from the U.N.’s Intergovernmental Panel on Climate Change warned, the planet could warm twice that amount or more.

Cities like New York are often more vulnerable to sudden downpours because so much of their land area is paved over with impervious surfaces like asphalt, which means that runoff is channeled into streets and sewers rather than being absorbed into the landscape.