Weather officials downgraded Hurricane Harvey to a tropical storm Aug. 26, yet catastrophic flooding continues to plague Southeast Texas in the wake of the storm. (Elyse Samuels/The Washington Post)

Weather officials downgraded Hurricane Harvey to a tropical storm Aug. 26, yet catastrophic flooding continues to plague Southeast Texas in the wake of the storm. (Elyse Samuels/The Washington Post)

More than 3,000 national and state guard troops are being deployed to assist with relief and recovery efforts as the nation’s fourth-largest city and surrounding areas try to cope with the aftermath of Hurricane Harvey, which has transformed into a disaster of historic proportions. President Trump plans to travel to Texas on Tuesday.

Gov. Greg Abbott (R) said in a news conference that the perpetual rain and dire flash flooding has produced the strongest storm the state has seen in at least 50 years. He could not confirm death totals nor the number of evacuations, but the National Weather Service has said there have been reports of as many as five deaths. The service issued a statement that the storm was “catastrophic” and “beyond anything experienced.”

Outside the Marriott Courtyard Hotel in Southwest Houston, Nichelle Mosby stood up to her knees in floodwater in the parking lot Sunday, 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 over the weekend, they booked into the Courtyard, where they are stranded with dozens of other guests.

1 of 74 Full Screen Autoplay Close Skip Ad × Hurricane Harvey makes landfall, slams South Texas View Photos Within hours after landfall as a Category 4 storm, Harvey weakened to Category 1, though “catastrophic” floods were still expected. Caption The hurricane, which has weakened to a tropical storm, is the first Category 4 storm to hit the United States since Charley in 2004. Harvey has destroyed homes, severed power supplies and caused severe flooding. Aug. 27, 2017 Two kayakers try to beat the current of an overflowing Brays Bayou in Houston. Rescuers answered hundreds of calls for help as floodwaters from the remnants of Hurricane Harvey began to fill second-story homes. Mark Mulligan/AP Buy Photo Wait 1 second to continue.

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

By Sunday afternoon, the Weather Service was predicting that parts of Texas could receive nearly 50 inches of rain, what would be the largest recorded total in the state’s history. Communities in Southeast Texas, already experiencing water so high that it engulfed vehicles up to their car handles, were continually being beaten down by heavy, sideways rain.

[FEMA director calls storm a ‘devastating disaster,’ says it could be the worst in Texas history]

The flood warnings also came with urgent pleas for residents to be cautious, stay indoors and not attempt to travel flooded roadways. Police and rescue workers implored residents who see floodwaters rising near their homes to make their way to the highest point possible — even if it is a roof — while awaiting rescue. On Saturday night, a woman was found dead near her vehicle, believed to have been trapped during a flood.

More than 82,000 homes were without electricity, and local news stations reported that Ben Taub Hospital, one of two trauma centers in the city, would soon have to evacuate.

The U.S. Coast Guard dispatched five helicopters, and Houston is expecting about 40 additional boats to find those in need of help, Mayor Sylvester Turner said in a news conference. He defended the decision not to issue evacuation orders, noting that it would have been 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.

As officials worked to execute a strategy, desperate families and residents crafted some of their own. At the urging of Houston police, they set out with boats and kayaks to help their friends in need. Families in flooded homes blew up inflatable pool toys to ferry children as they made their way out on foot.

In Katy, Erica Stietenroth, 38, said she was in tears driving around trying to find an open pharmacy to help her 8-year old daughter, who had a 105-degree fever. The emergency room on Saturday night didn’t have the drugs she needed for her strep throat, so doctors wrote her a prescription.

She awoke Sunday morning and started her desperate search, ultimately finding a pharmacy inside a local grocery store — but it was unstaffed because people couldn’t get in to work. An employee who happened to come in to shop for food got permission to mix the medication for her.

“I was crying my eyes out for my baby girl,” she said. “By the grace of God, that employee was there.”

By 7 a.m. Central time Sunday, the National Weather Service had recorded close to 25 inches of rain around Houston, with an additional three to seven inches expected. Warnings for flash flooding and tornadoes remained in place for a large swath of the state, and storm surges are expected along the coast, bringing flooding to typically dry areas. William H. Hobby Airport was shut down.

“There’s flooding all over this city,” Houston Police Chief Art Acevedo said in a live stream video early Sunday morning. “We have one fatality, and a potential second fatality from the floodwaters out here.”

William “Brock” Long, director of the Federal Emergency Management Agency, said he expects the agency to be working in the area for years as Texas recovers from the storm.

[‘All night of slam, bang, boom,’ then a scramble to assess the hurricane’s damage]

As it scrambles to open shelters across Texas, the Red Cross command center in Houston is now “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 around 7:30 a.m. Central time. He said most of the calls for help it has received have come from residents who tried to drive through the storm and wounded up getting stuck in high water.

President Trump praised the way the city’s officials are 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.”

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

Brown said the airport flooded so quickly that shuttles were unable to get to 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.”

In Southwest Houston, the Brays Bayou had overflown its banks and completely swamped a bridge near the hotel, with waters rising at least 10 to 20 feet or more since Saturday. Its powerful brown flow carried large tree branches and other debris.

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 possibly without power.

In the lobby of the Marriott Courtyard there, 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 stranded.

“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 station KHOU went offline while covering a live rescue of a driver in an 18-wheeler 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 evacuated because floodwaters seeped into the building.

Harvey pounded the Texas coast on Saturday, making landfall as a Category 4 hurricane that destroyed buildings and caused widespread power outages as residents evacuated towns. Later downgraded to a tropical storm, Harvey crept inland, then stalled and dropped hours of torrential rain that officials said has caused catastrophic flooding across a broad section of the state.

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 elderly neighbors they would probably be taking in from Grand Lakes, where they used to live.

They bought sheet cakes, 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 they live behind a creek and that all their neighborhood lakes were flooded. They said they were doing a grocery run in case the storm goes on for days.

“It’s gonna be a long haul,” said Picard, who was shopping for spring mix and frozen pizza with her husband and 6-year-old.

The small coastal town of Rockport, which took a direct hit from the storm, as search and rescue operations continued in ravaged areas that are still largely inaccessible. Officials said Rockport could receive as much as 60 inches of rain through midweek.

“We’ve been devastated,” Rockport Mayor C.J. Wax said in a telephone interview. “There are structures that are either significantly disrupted or completely destroyed. I have some buildings that are lying on the street.”

To the west, San Antonio Mayor Ron Nirenberg urged residents to continue to stay off the roads as Harvey neared the city and brought wind gusts of up to 60 mph and heavy rain. The city is under a flash flood watch and tropical storm warning.

“We don’t want anyone in San Antonio to let their guard down,” Nirenberg said.

The storm made landfall at 10 p.m. Central Time on Friday with 130 mph winds — the first Category 4 storm to hit the United States since Charley in 2004. By late morning Saturday, it had lost some of its punch but still had hurricane-force winds of 80 mph, having drifted to about 25 miles west of the inland city of Victoria. Shortly after noon, the National Hurricane Center downgraded Harvey to a tropical storm, with sustained winds of 70 mph.

Farther east, the hurricane has put officials in New Orleans and across Louisiana on alert, and Gov. John Bel Edwards (D) said Saturday that it could be a week before the state has to cope with flooding. He said the pumping system in New Orleans, which flooded earlier this month after a heavy downpour, is steadily improving. “We’re a long ways from being out of the woods, but we are very thankful it hasn’t been more severe up to now,” he said of the storm.

Trump signed a disaster proclamation for Texas on Friday night after Abbott sent him a written request saying that “Texas is about to experience one of the worst natural disasters in the history of the state.” White House aides said Trump will visit Texas soon.

Trump said in tweets Saturday morning that he is closely monitoring the situation from Camp David, Md., and that federal officials have been on the ground since before the storm hit. He urged residents to “be safe” and pledged a thorough federal response. “We are leaving nothing to chance,” he wrote. “City, State and Federal Govs. working great together!”

Sullivan reported from Houston, Galveston and Victoria. Baddour reported from Houston. Samuels reported from Washington. Tim Craig in Rockport and Corpus Christi, Brittney Martin in San Antonio, Ashley Cusick in New Orleans, Mary Lee Grant in Port Aransas, Tex., Sofia Sokolove in Austin, Emily Wax in Katy, Tex., and Joel Achenbach, Sandhya Somashekhar and Angela Fritz in Washington contributed to this report.