The full extent of Hurricane Harvey's aftermath started to come into chilling focus Sunday in Houston and across much of central Texas, as rain measured in feet, not inches, overwhelmed lakes, rivers and bayous, leaving several people dead and thousands displaced in a weather disaster described as "beyond anything experienced."

Across the nation's fourth-largest city and suburbs many miles away, families scrambled to get out of their fast-flooding homes. Rescuers — in many cases neighbors helping neighbors — in fishing boats, huge dump trucks and even front-end loaders battled driving rains to move people to shelter. Some used inflatable toys to ferry their families out of inundated neighborhoods, wading through chest-deep water on foot while the region was under near-constant tornado watches.

By Sunday afternoon, the National Weather Service — which tweeted the "beyond anything experienced" description that morning — was predicting that parts of Texas could receive nearly 50 inches of rain, the largest recorded total in the state's history. It also warned that Harvey's relentless downpours were expected to continue until late in the week and that flooding could become much more severe. More than 82,000 homes were without electricity in the Houston area by Sunday night as airports shuttered and hospitals planned evacuations.

Thousands of rescue missions have been launched across a large swath of Texas, and Gov. Greg Abbott, R, said Sunday that more than 4,000 National Guard troops had been deployed to assist with relief efforts. The Federal Emergency Management Agency said federal agencies have more than 5,000 employees working in Texas, and the White House said President Trump plans to visit parts of the state on Tuesday.

Officials said Houston, a major center for the nation's energy industry, had suffered billions of dollars in damage and would take years to fully recover. Oil and gas companies have shut down about a quarter of oil and gas production in the Gulf of Mexico. Spot prices for gasoline are expected to jump on Monday, but the full extent of damage will not be clear for days, companies and experts said.

Harvey's sheer size also became apparent Sunday as heavy rains and flooding were reported as far away as Austin and even Dallas. What started with a direct impact on the tiny coastal town of Rockport on Friday night has turned into a weather disaster affecting thousands of square miles and millions of people.

In Austin, the Wilhelmina Delco Center, one of two Red Cross shelters in the city, had about 200 evacuees. Rain continued to fall steadily in Austin on Sunday, and river levels continued to rise. Precautionary sandbags were stacked against the shelter's entrance.

Bristel Minsker, communications director for the Red Cross Central and South Texas region, said "things are changing quickly" as the organization prepares to scale up operations in the areas between Austin and Houston.

Still, much of the nation's focus remained squarely on Houston, where the massive scale of the flooding and the potential for it to get much worse in the days ahead was reminding many spooked residents of the effects of Hurricane Katrina on New Orleans.

Mayor Sylvester Turner and other officials pleaded with residents to "shelter in place" and to make calls to overwhelmed 911 operators only in life-threatening emergencies. They urged people to climb to their roofs to await shelter if water was rising in their homes, and local TV news anchors reminded people to stay out of attics where they might be trapped by water — or to take an ax to hack their way to the roof.

Police began to ask people with high-water vehicles and boats to assist in rescue efforts on streets where abandoned cars were completely submerged. Brays Bayou, a huge waterway crossing the southwestern part of the city, rose between 10 and 20 feet overnight and by Sunday morning was flowing over bridges in its path.

The Texas National Guard has deployed across the state, including engineers in Corpus Christi and an infantry search-and-rescue team in Rockport. Another search-and-rescue unit was staging in San Antonio and was likely to be deployed to affected areas shortly, officials said.

As the extent of the disaster became clear at daylight Sunday, some criticized Houston officials for not calling for an evacuation of the city. Turner defended the decision not to evacuate, noting that it would be a "nightmare" to empty out the population of his city and the county all at once.

"You literally cannot put 6.5 million people on the road," Turner said at a news conference.

Trump praised the way the city's officials were handling the flood, tweeting at 8:25 a.m. that the "Good news is that we have great talent on the ground." He promised to head to Texas "as soon as that trip can be made without causing disruption. The focus must be life and safety." Trump signed a disaster proclamation for Texas on Friday night.

The disaster unfolding in Houston appeared suddenly, starting with severe storms Saturday evening that came with slashing, sideways rain and almost uninterrupted lightning. By morning, a city that had been largely spared by Harvey's initial pounding of coastal communities was flooded to devastating levels.

By 7 a.m. Central time, the National Weather Service had recorded close to 25 inches of rain around Houston. Warnings for flash flooding and tornadoes remained across the region, and storm surges were expected along the coast, bringing flooding to typically dry areas.

The Weather Service said Sunday that at least five people had been reported dead because of Harvey. Local officials have confirmed that at least three people have died as a result of the storm, and officials in the hardest-hit counties expect that as the waters recede the number of fatalities will rise.

The first reported death came Saturday in Rockport. Officials said one person was killed after becoming stuck inside a house that caught fire during the storm.

About 9:15 p.m. on Saturday, rescuers in southwest Houston recovered the body of a woman thought to have driven her car into floodwaters before attempting to escape on foot. Just two minutes earlier, police about 40 miles southeast in La Marque found the body of a 52-year-old homeless man in a Walmart parking lot where there had been high water.

"No city can handle these kind of deluges. In our case, 23 inches overnight," La Marque Mayor Bobby Hocking said Sunday, noting that the police department rescued approximately 30 families and brought them to city offices. "I have since secured hotel rooms for them. They were thankful and cried tears of joy," he said.

As it scrambled to open shelters across Texas, the Red Cross command center in Houston was "physically isolated" because of floodwaters, said Paul Carden, district director of Red Cross activities in south Texas, which includes Corpus Christi.

"The advice is, if you don't have to be out, don't be out," said Bill Begley, a spokesman with the Joint Information Center in Houston. He said most of the calls for help the center had received had come from residents who tried to drive through the storm and got stuck in high water.

Both of Houston's major airports were closed, and many tourists and visitors found themselves stranded in hotels with no hope of leaving anytime soon.

Southwest Airlines flight attendant Allison Brown said at least 50 flight attendants, a number of pilots, airport staff and hundreds of passengers have been stranded at William P. Hobby Airport since at least 1 a.m. Sunday.

Brown said the airport flooded so quickly that shuttles were unable to get them out. They were told by police that it would be unsafe to attempt to leave.

"Luckily, we have the restaurant staff, or else we would've been stuck with no food," Brown said. "Waters in the road are around four feet - minimum - surrounding the airport."

The Marriott Courtyard Hotel in southwest Houston, along the banks of Brays Bayou, was surrounded by floodwater when guests woke up Sunday morning.

All roads in the area were underwater, and a park across the bayou was completely flooded. A car nearby had been abandoned, its doors left open. City traffic lights were still blinking red and green over the empty and flooded bridge, but most buildings visible in the area seemed to be dark and without power.

Water covered about eight blocks on the edge of Houston's downtown, entering the ground floors of the Wortham Center, a downtown theater, and the historic Lancaster Hotel, where staff members were still posted to ward off looters. A Chase bank branch was submerged in flowing water that reached almost to its roof.

By midmorning, Nichelle Mosby stood up to her knees in floodwater in the parking lot, grimacing with a towel over her head to block the rain. Mosby and six family members, including a 4-year-old girl, had come from Louisiana to visit relatives. When Harvey hit, they booked into the Courtyard. Now they were stranded with dozens of other guests.

"We went through Katrina, but this feels different," she said. Instead of a gradual buildup of water, she said, "this was like a gush of water that came up too fast."

In the lobby, John McMillian, 70, sat eating breakfast with his wife, Debbie McMillian, 64, and their daughter, Tara, 29.

They were in town so John McMillian could have five days of treatment for his leukemia at MD Anderson Cancer Center just down the road. He had three days of treatment and was supposed to have his fourth on Sunday, but now they were marooned.

"If push came to shove, we could always wade to the hospital," he said.

"I'm not going to let him, don't worry," his wife added.

She said her new Acura was underwater in the parking lot.

"I haven't even made the first payment on it yet," she said.

Local television station KHOU went offline while covering the rescue of a driver in an semitrailer stuck in more than 10 feet of water near the Interstate 610 loop. The reporter was able to flag down a rescue crew, but as the rescue was about to take place, the station went dark. The main office said the station had to evacuate because floodwaters rushed into the building.

Local television and the Weather Channel showed rescues by boat, including in Dickinson, south of Houston on the way to Galveston, which appeared to be completely inundated.

"This place was built in 1976, and this has never happened," the owner of a flooded RV park told a reporter. Asked where people would go once they were rescued from their RVs, she said, "I have no idea."

About 500 displaced people are now living in two shelters in Dallas, 240 miles north of Houston.

In one, a neighborhood recreation center on the far south side of Dallas, Rebecca Hernandez, 35, said she and her family came from their north Houston home to avoid floodwaters. She, her husband, Gilbert, and their three children drove to Dallas on Friday night. With rent due in a few days, the family couldn't afford to spend more than one night in a hotel, so they came here.

"We're starting small," said Angienetta Johnson, who runs the shelter, noting that there were perhaps 500 or so evacuees in her shelter and another one across town. "But we have plans to go up to 5,000 if need be."

A neighbor has told Hernandez that floodwaters were at the family's front door Sunday - just as they were during Katrina.

"We're ready to go back as soon as they tell us it's safe," she said.

In Katy, Michele and Joel Antonini were in line at a cavernous HEB supermarket with 20 sacks of groceries. They had come out in the rain to buy food for neighbors they would probably be taking in from Grand Lakes, where they used to live.

They bought a sheet cake, a roast, chips, hot dogs and hamburgers.

"We just want to be ready if they are hungry and can get out," Michele said. "We just want to be ready to help."

Amanda Picard, 35, a CrossFit trainer, said that she lives behind a creek and that all the neighborhood lakes were flooded. She said she was doing a grocery run, picking up spring mix and a frozen pizza, with her husband and 6-year-old in case the storm goes on for days.

"It's gonna be a long haul," Picard said.