CRAWFORDVILLE, Fla. (AP) — Emergency crews rushed Friday to rescue people trapped in flooded homes after Helene roared ashore as a powerful Category 4 hurricane in Florida, generating a massive storm surge and knocking out power to millions of customers in several states. At least 21 people were reported dead in four states.

Georgia Gov. Brian Kemp said dozens of people were still trapped in buildings damaged by Helene. Authorities were "having a hard time getting to places" so teams with chainsaws were "working to free up roads," Kemp told a news conference.

The storm made landfall late Thursday in a sparsely populated region with maximum sustained winds of 140 mph (225 kph) in the rural Big Bend area, home to fishing villages and vacation hideaways where Florida's Panhandle and peninsula meet. But the damage extended hundreds of miles to the north, with flooding as far away as North Carolina, where a lake used in scenes from the movie "Dirty Dancing" overtopped a dam. Multiple hospitals in southern Georgia were without power, and one in Tennessee was closed.

"Thank God we're both alive to tell about it," Rhonda Bell said after a towering oak tree outside her home in Valdosta, Georgia, smashed through the roof.

Video on social media sites showed sheets of rain coming down and siding coming off buildings in Perry, Florida, near where the storm arrived. One local news station showed a home that was overturned, and many communities established curfews.

"It's really heartbreaking," said Stephen Tucker, after the hurricane peeled off the brand-new roof at her church in Perry, Florida. It had to be replaced after last year's Hurricane Idalia.

Florida Gov. Ron DeSantis said the damage from Helene in the area appears to be greater than the combined damage of Idalia and Hurricane Debby in August. "It's demoralizing," he said.

President Joe Biden said he was praying for survivors as the head of the Federal Emergency Management Agency headed to the area. The agency has deployed more than 1,500 workers, and they helped with 400 rescues by late morning.

Many of the stranded in places like Tampa could be reached only by boat, with officials elsewhere warning that the water could contain live wires, sewage, sharp objects and other debris.

"If you are trapped and need help please call for rescuers – DO NOT TRY TO TREAD FLOODWATERS YOURSELF," the sheriff's office in Citrus County, Florida, warned in a Facebook post, while raising concerns that the tide could bring another surge of up to 10 feet (3.05 meters).

More than 4 million homes and businesses were without power Friday morning in Florida, Georgia and South Carolina, according to poweroutage.us, which tracks utility reports.

Kemp said at least 11 people in his state were killed. At least six others died in South Carolina, two in in Florida and two in North Carolina.

Among the dead was one person killed in Florida when a sign fell on their car. Two others were reported killed in a possible tornado in southern Georgia as the storm approached.

The hurricane came ashore near the mouth of the Aucilla River on Florida's Gulf Coast. That location was only about 20 miles (32 kilometers) northwest of where Idalia hit last year at nearly the same ferocity and caused widespread damage.

Cities as far inland as Atlanta were drenched, with just mailboxes and car roofs poking out of the water in some neighborhoods. Kemp mobilized an additional 1,000 National Guard troops, on top of the 500 he mobilized earlier.

As the hurricane's eye passed near Valdosta, a city of 55,000 near the Florida line, dozens of people huddled early Friday in a darkened hotel lobby. While the wind howled outside, water dripped from light fixtures in the lobby dining area.

Fermin Herrera, 20, his wife and their 2-month-old daughter left their room on the top floor of the hotel, where they took shelter because they were concerned about trees falling on their Valdosta home.

"We heard some rumbling," said Herrera, cradling the sleeping baby in a downstairs hallway.

Helene is the third storm to strike the city in just over a year. Tropical Storm Debby blacked out power to thousands in August, while Hurricane Idalia damaged an estimated 1,000 homes in Valdosta and surrounding Lowndes County a year ago. Now some downtown storefront windows were shattered and store awnings mangled.

Soon after it crossed over land, Helene weakened to a tropical storm, with its maximum sustained winds falling to 70 mph (110 kph). At 11 a.m. Friday, the storm was about 105 miles (165 kilometers) northeast of Atlanta, moving north at 32 mph (52 kph) with maximum sustained winds of 45 mph (75 kph), the National Hurricane Center in Miami reported.

Forecasters expected the system to continue weakening as it moves into Tennessee and Kentucky and drops heavy rain over the Appalachian Mountains, with the risk of mudslides and flash flooding.

Even before landfall, the storm's wrath was felt widely, with sustained tropical storm-force winds and hurricane-force gusts along Florida's west coast. Officials begged residents to evacuate.

"Please write your name, birthday, and important information on your arm or leg in a PERMANENT MARKER so that you can be identified and family notified," the sheriff's office in mostly rural Taylor County, Florida, warned those who chose not to evacuate in a Facebook post. The dire advice was similar to what other officials have dolled out during past hurricanes.

Beyond Florida, up to 10 inches (25 centimeters) of rain had fallen in the North Carolina mountains, with up to 14 inches (36 centimeters) more possible before the deluge ends, setting the stage for flooding that forecasters warned could be worse than anything seen in the past century. Evacuations were underway in several areas of the state Friday, and around 300 roads were closed.

The Connecticut Army National Guard sent a helicopter to help in the state.

"It's terrible. I don't know if I will ever see anything like this again," said Spencer Tate Andrews, of Asheville, North Carolina.

School districts and multiple universities canceled classes. Airports in Florida that closed were to reopen Friday, and inspectors were out examining bridges and causeways along the Gulf Coast to get them back open to traffic quickly, the state's transportation secretary said.

A day before hitting the U.S., Helene swamped parts of Mexico's Yucatan Peninsula, flooding streets and toppling trees as it brushed the resort city of Cancun and passed offshore. In western Cuba, Helene knocked out power to more than 200,000 homes and businesses as it brushed past the island.

Helene was the eighth named storm of the Atlantic hurricane season, which began June 1. The National Oceanic and Atmospheric Administration has predicted an above-average Atlantic hurricane season this year because of record-warm ocean temperatures.

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Payne reported from Tallahassee, Florida, and Hollingsworth reported from Kansas City, Missouri. Associated Press journalists Seth Borenstein in New York; Jeff Amy in Atlanta; Russ Bynum in Valdosta, Georgia; Danica Coto in San Juan, Puerto Rico; Andrea Rodríguez in Havana; Mark Stevenson and María Verza in Mexico City; and Claire Rush in Portland, Oregon, contributed to this report.