The largest search and rescue mission in US history is running into trouble as obstacles left behind by the passage of Hurricane Ian hamper efforts.
At least 77 people have been confirmed dead in the storm's wake, as it continues from Florida into North Carolina.
The largest impacts remain in Florida, where river flooding may continue inland well into next week, forecasters warn.
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At Florida's ground zero, Fort Myers, the only highway into town, the I75, has been cut off by flooding.
Traffic is banked up for 16km, meaning crucial food, fuel and other supplies can't get into the ravaged town.
People trapped in their cars amid the floodwaters are having to be lifted to safety by the US Coast Guard.
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Online cameras showed seawater filling neighbourhoods in Garden City to calf level. As Ian moved across South Carolina on its way to North Carolina Friday evening, it dropped from a hurricane to a post-tropical cyclone.
Ian left a broad swath of destruction in Florida, flooding areas on both of its coasts, tearing homes from their slabs, demolishing beachfront businesses and leaving more than 2 million people without power.
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In Florida's hard-hit Fort Myers Beach, where a furious storm surge wiped out homes and left little but debris, shaken survivors are coping with what they saw and mourning those they've lost.
Kevin Behen, who rode out the storm on the second floor of a building in Fort Myers Beach, told CNN Friday night he knew of two men who died making sure their wives escaped a home that had begun to flood.
"These guys pushed their wives out the windows to where a tree was," Behen said. "They just looked at their wives and they said, 'We can't hold on anymore, we love you. Bye,' and that was it."
About 90 per cent of the island "is pretty much gone," Fort Myers Beach Town Councilman Dan Allers said Friday.
"Unless you have a high-rise condo or a newer concrete home that is built to the same standards today, your house is pretty much gone."
Many of the deaths were drownings, including that of a 68-year-old woman swept away into the ocean by a wave. A 67-year-old man, who was waiting to be rescued, died after falling into rising water inside his home authorities said.
Other storm-related fatalities included a 22-year-old woman who died after an ATV rollover from a road washout and a 71-year-old man who fell off a roof while putting up rain shutters. An 80-year-old woman and a 94-year-old man who relied on oxygen machines also died after the equipment stopped working during power outages.
Another three people died in Cuba earlier in the week as the storm churned northward. The death toll was expected to increase substantially once emergency officials have an opportunity to search many of the hardest-hit areas.
Rescue crews piloted boats and waded through riverine streets in Florida after the storm to save thousands of people trapped amid flooded homes and shattered buildings .
Hurricane Ian has likely caused "well over $100 billion'' in damage, including $US63 billion ($98 billion) in privately insured losses, according to the disaster modeling firm Karen Clark & Company, which regularly issues flash catastrophe estimates. If those numbers are borne out, that would make Ian at least the fourth costliest hurricane in US history.
Florida Division of Emergency Management Director Kevin Guthrie said first responders have focused so far on "hasty" searches, aimed at emergency rescues and initial assessments, which will be followed by two additional waves of searches. Initial responders who come across possible remains are leaving them without confirming, he said Friday, describing as an example the case of a submerged home.
"The water was up over the rooftop, right, but we had a Coast Guard rescue swimmer swim down into it and he could identify that it appeared to be human remains. We do not know exactly how many," Guthrie said.
Desperate to locate and rescue their loved ones, social media users shared phone numbers, addresses and photos of their family members and friends online for anyone who can check on them.
Orlando residents returned to flooded homes Friday, rolling up their pants to wade through muddy, knee-high water in their streets.
Friends of Ramon Rodriguez dropped off ice, bottled water and hot coffee at the entrance to his subdivision, where 10 of the 50 homes were flooded and the road looked like a lake. He had no power or food at his house, and his car was trapped by the water.
"There's water everywhere," Rodriguez said. "The situation here is pretty bad."
The devastating storm surge destroyed many older homes on the barrier island of Sanibel, Florida, and gouged crevices into its sand dunes. Taller condominium buildings were intact but with the bottom floor blown out. Trees and utility poles were strewn everywhere.
Satellite images show level of damage
Municipal rescuers, private teams and the Coast Guard used boats and helicopters Friday to evacuate residents who stayed for the storm and then were cut off from the mainland when a causeway collapsed. Satellite images show the degree of damage.
Volunteers who went to the island on personal watercraft helped escort an elderly couple to an area where Coast Guard rescuers took them aboard a helicopter.
Hours after weakening to a tropical storm while crossing the Florida peninsula, Ian regained strength Thursday evening over the Atlantic. Ian made landfall in South Carolina with maximum sustained winds of 140 km/h. When it hit Florida's Gulf Coast on Wednesday, it was a powerful Category 4 hurricane with 240 km/h.
After the heaviest of the rainfall blew through Charleston, Will Shalosky examined a large elm tree in front of his house that had fallen across his downtown street. He noted the damage could have been much worse.
"If this tree has fallen a different way, it would be in our house," Shalosky said. "It's pretty scary, pretty jarring."
Ian's heavy rains and winds of 40km/h were near the North Carolina-Virginia state line at 11am Saturday (1am Sunday AEST) after crossing into North Carolina on Friday evening (Saturday AEST). Gov. Roy Cooper warned residents to be vigilant, given that up to 20.3cm of rain could fall in some areas.
"Hurricane Ian is at our door. Expect drenching rain and sustained heavy winds over most of our state," Cooper said. "Our message today is simple: Be smart and be safe."
In Washington, President Joe Biden said he was directing "every possible action be taken to save lives and get help to survivors."
"It's going to take months, years to rebuild," Biden said.
"I just want the people of Florida to know, we see what you're going through and we're with you."
Not just those directly impacted are suffering
The floods in North Port show the impact of Ian has not been confined to the beaches and tourist towns. The heavy rains from the storm have ended up flowing into suburban and inland towns not part of hurricane warnings.
It's the rising rivers that do it because of the hurricane's deluge, which continues to cause havoc long after the winds have passed. And it's leading to rescue efforts not that different from those on the coasts.
Floods were reported all across the center of the state: around Orlando and its theme parks, south to Kissimmee, east to Daytona Beach, Arcadia cattle country. People near rivers were deeply affected.
Near North Port, the Florida Department of Transportation closed a stretch of Interstate 75 in both directions late Friday because of the flooded Myakka River.
Dozens of National Guardsmen arrived earlier Friday in North Port— about 140 kilometres south of Tampa — to speed up efforts started Wednesday by firefighters from other states and counties. And city officials were scrambling to open an evacuation center at a high school.
Just west of North Port, the Myakka River was forecast by the National Weather Service to reach record flood stage Friday at 3.8 meters and then crest a bit higher before receding.
The nearby Peace River was set to hit an even higher mark: almost 7.3 meters, which is about twice the previous record. It runs through mainly rural areas, especially the cattle town of Arcadia which is home to a well-known Florida rodeo.
