(CNN) - Hurricane Florence's rainfall has stopped, but its "nightmare" destruction isn't over yet.
On Wednesday, thousands of evacuees were urged to stay away from their homes, some rivers kept rising, and the threat of floods remained high in North and South Carolina. Many roads remained closed, and thousands of people lacked power.
President Donald Trump spoke with state and federal officials at Marine Corps Air Station Cherry Point on the Neuse River in North Carolina. He praised first responders and said the country mourns with the families of the at least 36 people killed by Florence.
"Our state took a gut punch and our state is still reeling," North Carolina Gov. Roy Cooper told Trump, calling the storm "epic, disastrous and widespread."
"We've got a long road ahead in the days, in the months and even years ahead to make sure we build back."
The President said the federal government would do everything necessary to ensure recovery. "America grieves with you and our hearts break for you," Trump said. "God bless you. We will never forget your loss. To all those impacted by this terrible storm, our entire American family is with you and ready to help. You will recover."
Later he traveled to Conway, South Carolina, where Gov. Henry McMaster met the President as he arrived.
Also across the ravaged region:
• Rivers are still rising in South Carolina and will continue throughout the week, the state's Emergency Response Team said Wednesday morning. • Some 2,600 National Guard men and women are deployed across the state. • About 800 power outages have occurred in South Carolina. • North Carolina farms lost an estimated 3.4 million poultry birds and 5,500 pigs, officials said. • South Carolina cotton farmers also were hit hard. Soaked ground could damage peanut crops, and hemp stems were reported blown over, the state said.
Among the dead were two detainees who died in a Horry County Sheriff's Office transportation van in South Carolina floodwaters.
Much work remains in the recovery efforts, officials said.
Crews must work to reopen roads, restore power, contain hazardous materials and restore medical services, Federal Emergency Management Agency Administrator Brock Long said at Cherry Point.
Rivers cresting, some twice
North Carolina's Cape Fear River reached 61 feet near Fayetteville on Wednesday, putting thousands in harm's way.
Toward the coast, Brunswick County Sheriff John Ingram said in a Facebook video that officers are going door-to-door in the Waccamaw River floodplain areas to encourage residents to consider evacuating and to get ready in case it becomes necessary.
Many were outside enjoying the beautiful weather Wednesday, he said. But already the water is 3 feet higher than normal.
"We want to make sure everyone has adequate time to evacuate if these waters continue to rise and crest at the forecasted levels," he said.
Floodwaters rose and then receded in Conway, South Carolina, but a second cresting is expected.
Greenville News reporter Gabe Cavallaro tweeted photos comparing a flooded street that had since returned to normal.
"Recognize this place?" he tweeted. "Amazing. Just days before this #ConwaySC neighborhood was completely underwater - now floodwaters from #Florence have receded and the road is back open again. But city officials warn that it won't last long, as levels in the Waccamaw River creep higher."
City spokesman Taylor Newell said the waters could be "4 feet higher" than when Hurricane Matthew struck in 2016.
"We are cautioning everyone not to be overconfident," City Administrator Adam Emrick said. "The water is going to come back up. We are worried about Friday."
Trump met with first responders at the Horry County Emergency Operations Center.
"It's going to get rough for South Carolina," he warned ahead of the expected cresting of rivers.
"You're going to have a rebuilding process, and we are behind you from day one," Trump said, calling this the "calm before the storm, because you're going to have a lot of water."
Some returning home to devastation
On Tuesday, after days of hoping for the best, Billy and Rita Sanderson waded in knee-high murky waters to see Florence's storm damage to their home of nearly 30 years.
They passed a car buried in floodwaters and called out to see if anyone was in it. When no one answered, they turned their attention to their white house with dark shutters -- partially submerged in the water in front of them.
"That thing is a total loss," Billy Sanderson told CNN affiliate WNCT, his voice breaking. "It's just hard to explain. You're going to have to start over, that's all we can do."
Florence slammed into the North Carolina coast last week as a Category 1 hurricane, and has killed at least 36 people, authorities said. Of those, 27 died in North Carolina, including in Duplin County, where the Sandersons live. Eight others died in South Carolina, and an additional person was killed in a storm-related tornado in Virginia.
Governor to evacuees: Don't go back home
Cooper warned residents that the rain may have subsided, but the flooding danger is far from over. He asked evacuees to stay where they are and not return home just yet.
"To the approximately 10,000 people staying in our shelters and the countless more who are staying with friends and families or in hotels, I know it was hard to leave home and it's even harder to wait," Cooper said. "Please ... do not try to return home yet."
Evacuees from Pender and Brunswick counties should especially not go home due to flooding, he said.
More than 800 roads were closed across North Carolina on Wednesday, officials said, and about 172,000 homes and businesses were still without power.
Swollen rivers mean danger remains
Fayetteville City Manager Doug Hewett said he's concerned that with the rain gone, residents may become complacent and try to get back home, which could be dangerous.
"We have 12,000 residents who could be in harm's way if the river continues to rise," he said.
Hewett said the Cape Fear River could crest to its highest historic level -- about 62 feet -- by Wednesday.
"We had significant rainfall ... and we're still anticipating that some of the tributaries are draining into the upper Cape Fear. And if that happens, it will continue to rise until it crests," he said.
Wilmington was the epicenter of Florence's destruction. Rainfall totals of 26.58 inches submerged much of the city, cutting it off from the rest of the state. It will have its wettest year in 140 years of record-keeping. More than 86 inches of rain have fallen so far. On average, the city gets about 43 inches by this time of the year.
In Lumberton, where residents scrambled to plug the levee system, parts of Interstate 95 will remain closed until the Lumber River drops below 21 feet. That might not happen until next week, said Corey Walters, the city's deputy director of public works.
But it's impossible to say how deep the Lumber River is now, because the official river gauge stopped working a few days ago. Walters estimated the current depth is about 25 feet.