NASHVILLE, Tenn. (AP) — As floodwaters from Hurricane Helene quickly surrounded a small Tennessee hospital near a riverbank, workers first tried to get patients out by ambulance. Then, the road washed out.

They tried to move people to the center of the low-slung building, but they were met by water.

Once rescue boats arrived, the water was so dangerous they couldn't leave. Ultimately, dozens of staff and patients went to the roof to wait to be taken to safety, and a few others stayed in rescue boats, as winds whipped and brown waters gushed nearby with debris beneath them.

Within a few hours, they were all rescued.

The dramatic scene at Unicoi County Hospital, in Erwin, Tennessee, near the North Carolina border, was one of several that played out across the southern U.S. in Helene's wake. Flooding caused by its storm surge and rain sent thousands of police officers, firefighters, National Guard members and others on rescue missions. Hundreds were saved, but at least 40 died.

"It was just the grace of God we had ample amount of people to move people up to the roof," Jennifer Harrah, the Tennessee hospital's administrator, told WJHL-TV. "And we were able to put the non-ambulatory patients in the boats and keep them safe and have medical personnel with the patients in the boats as well. And we kind of had them in a corner, protected by a couple of walls."

Unicoi County Hospital tried to evacuate 11 patients and dozens of others Friday morning after the Nolichucky River overflowed its banks and flooded the facility, but the water was too treacherous for boats sent by the Tennessee Emergency Management Agency.

The decision was made to direct more than 50 people to the roof. Another seven had been temporarily stuck in rescue boats. Ballad Health, which operates the small 10-bed hospital, asked for people's prayers as it provided the social media update.

After other helicopters failed to reach the hospital because of the storm's winds, a Virginia State Police helicopter was able to land on the roof. Three National Guard helicopters with hoist capabilities were sent and Ballad Health assisted with its own helicopter, officials said.

In a later post, Ballad Health said all of the staff and patients had been rescued about four hours after dozens of them were moved to the hospital's roof. Patients were transferred to a different facility and no one remained at the hospital.

"The water there simply came up faster with more debris than was safe to operate in the rafts to ferry from a dry point back to the hospital," said Patrick Sheehan, Tennessee's emergency operations director.

Meanwhile in Florida, the efforts of 1,500 search-and-rescue personnel will be concentrated on securing and stabilizing affected communities through the weekend, said Kevin Guthrie, the state's emergency operations director. The Category 4 storm made landfall on the Northwest Florida coast late Thursday, but it created flooding from storm surge all along the state's Gulf Coast.

"As those sorts of rescue missions happen today, and continue, please do not go out and visit the impacted areas," Guthrie said at a Friday news conference in the Florida capital of Tallahassee. "I beg of you, do not get in their way."

The reported rescues ranged from life-threatening situations to people trapped in their homes by waist-high water and unable to flee on their own.

Five people died in Pinellas County and dozens were rescued after the storm surge hit an unprecedented 8 feet (2.4 meters), forcing some to seek shelter in their attics. Sheriff Bob Gualtieri said the deaths all occurred in neighborhoods where authorities told residents to evacuate, but many ignored the warnings.

He said survivors told deputies they didn't believe the warnings after other residents told them the surge wouldn't be that bad.

"We made our case. We told people what they needed to do, and they chose otherwise," Gualtieri said.

Gualtieri said his deputies tried overnight to reach those who had been trapped, but in some neighborhoods it just wasn't safe. Pinellas County includes St. Petersburg.

"I was out there personally. We tried to launch boats, we tried to use high-water vehicles and we just met with too many obstacles," Gualtieri said. He said the death toll could rise as emergency crews go door-to-door in the flooded areas to see if anyone remains.

In neighboring Hillsborough County, which includes Tampa, the sheriff's office rescued more than 300 people overnight from storm surge. Spokesperson Amanda Granit said those included a 97-year-old woman with dementia and her 63-year-old daughter, who got surprised by the surge and needed help fleeing their flooded home; and a 19-year-old woman whose car got stuck as she drove in the rising water and couldn't get out.

Granit said deputies were conducting rescues in such large numbers they had to request county transit buses to get the people to safety.

"Deputies couldn't move them fast in enough in their patrol vehicles," Granit said.

In the Tampa Bay-area city of South Pasadena, rescue video shows a house burning early Friday amid flooded streets. Other counties along the Gulf reported more than 100 rescues.

When water from the storm surge reached Kera O'Neil's knees inside her Hudson home, 45 miles north of Tampa, she knew she and her sister needed to flee with her two cats.

"There's a moment where you are thinking if this water rises above the level of the stove, we are not going to have much room to breathe," she said.

O'Neil and her sister waded into the chest-deep water with one cat in a plastic carrier and another in a cardboard box. They found refuge on a neighbor's more elevated property before Pasco County firefighters on a raft rescued them and three others.

"I'm a Florida girl, and we have been here since we were kids," she said. "We have never experienced anything like this."

At sea, the Coast Guard said it rescued three boaters and their pets from the storm in separate incidents. In a Thursday helicopter rescue captured on Coast Guard video, a man and his Irish setter were stranded 25 miles offshore in the Gulf on their 36-foot sailboat in heavy seas.

The video shows the man putting his dog into a yellow rescue vest and pushing it into the raging sea before jumping in himself. A Coast Guard swimmer helped them into a rescue basket and they were hoisted into the copter.

In North Carolina, more than 100 swift-water rescues had occurred as Helene's rains caused massive flooding Friday, particularly in the state's western section. Gov. Roy Cooper said the flash floods are threatening lives and are creating numerous landslides.

"The priority now is saving lives," Cooper said, begging people to stay off the roads unless they were seeking higher ground.

"With the rain that they already had been experiencing before Helene's arrival, this is one of the worst storms in modern history for parts of western North Carolina," Cooper said.

In Georgia, Gov. Brian Kemp said crews are working to rescue people trapped in more than 115 homes.

Helene's rains flooded homes in Hanover West, a neighborhood in north Atlanta. Emergency personnel rescued several people from their homes, said Richard Simms, a resident in a nearby neighborhood.

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Spencer reported from Fort Lauderdale, Florida. Associated Press reporter Beatrice Dupuy contributed to this report.