Hurricane Helene is barreling through the southeastern US after smashing the Florida coastline with 140mph winds and leaving a trail of destruction in its wake. 

But one heartwarming story has already emerged from the chaos - the moment the US coastguard pulled off a daring rescue of a stranded sailor and his loyal dog.

The companions found themselves in a perilous situation when their 36-foot vessel became disabled and began taking on water in the Gulf of Mexico yesterday. 

Facing the wrath of the approaching hurricane, the sailor sent out a distress call that was picked up by the vigilant USCG Air Station Clearwater, before they were forced to jump into the raging seas.

With the storm bearing down, Coast Guard crews raced against time to reach the man, located roughly 25 miles offshore from Sanibel Island near Fort Myers. 

Despite the mounting waves and violent winds, the skilled crew executed a flawless rescue, hoisting both the sailor and his faithful friend to safety - but not before one rescuer managed to snap a remarkable image of the pair in the water as the chopper soared overhead. 

Hurricane Helene made landfall in northwestern Florida as a Category 4 storm, battering the coast with torrential rain and punishing gusts as residents across the southeastern US braced for what forecasters warned would be a 'nightmare storm'. 

Helene roared ashore around 11:10pm CDT last night with maximum sustained winds of 140 mph.

It hit near the mouth of the Aucilla River in the Big Bend area of Florida's Gulf Coast - just 20 miles northwest of where Hurricane Idalia came ashore last year at nearly the same ferocity and caused widespread damage.

Helene prompted hurricane and flash flood warnings extending far beyond the coast up into northern Georgia and western North Carolina. 

More than 1.2 million homes and businesses were without power in Florida, more than 190,000 in Georgia and more than 30,000 in the Carolinas, according to the tracking site poweroutage.us. 

The governors of those states and Alabama and Virginia all declared emergencies.

At least three people have been killed so far - one person died in Florida when a sign fell on their car and two people were reported killed in a possible tornado in south Georgia as the storm approached.

'When Floridians wake up tomorrow morning, we're going to be waking up to a state where very likely there's been additional loss of life and certainly there's going to be loss of property,' Florida Gov. Ron DeSantis said at a news conference Thursday night.

Helene was early Friday downgraded to a Category 2 storm but has already left a trail of destruction in its wake.  

Helene was moving rapidly inland after making landfall, with the center of the storm set to race from southern to northern Georgia through early Friday morning. 

The risk of tornadoes also would continue overnight and into the morning across north and central Florida, Georgia, South Carolina and southern North Carolina, forecasters said. 

'Helene continues to produce catastrophic winds that are now pushing into southern Georgia,' the hurricane center said in an update at 1 a.m. Friday. 

'Persons should not leave their shelters and remain in place through the passage of these life-threatening conditions.'

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. 

Water lapped over a road in Siesta Key near Sarasota and covered some intersections in St. Pete Beach. Lumber and other debris from a fire in Cedar Key a week ago crashed ashore in the rising water.

Beyond Florida, up to 10 inches of rain had fallen in the North Carolina mountains, with up to 14 inches more possible before the deluge ends, setting the stage for flooding that forecasters warned could be worse than anything seen in the past century.

Heavy rains began falling and winds were picking up earlier Thursday in Valdosta, Georgia, near the Florida state line. 

The weather service said more than a dozen Georgia counties could see hurricane-force winds exceeding 110 mph (177 kph).

In south Georgia, two people were killed when a possible tornado struck a mobile home on Thursday night, Wheeler County Sheriff Randy Rigdon told WMAZ-TV. Wheeler County is about 70 miles southeast of Macon.

The storm made landfall in the sparsely-populated Big Bend area, home to fishing villages and vacation hideaways where Florida's Panhandle and peninsula meet.

In an unsettling post on Facebook, the sheriff's office in rural Taylor County warned residents who had not evacuated: '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.'

Federal authorities staged search-and-rescue teams as the weather service forecast storm surges of up to 20 feet and warned they could be particularly 'catastrophic and unsurvivable' in Apalachee Bay.

'Please, please, please take any evacuation orders seriously!' the office said, describing the surge scenario as 'a nightmare.'

This stretch of Florida known as the Forgotten Coast has been largely spared by the widespread condo development and commercialization that dominates so many of Florida's beach communities. 

The region is loved for its natural wonders - the vast stretches of salt marshes, tidal pools and barrier islands.

'You live down here, you run the risk of losing everything to a bad storm,' said Anthony Godwin, who lives about a half-mile from the water in the coastal town of Panacea, as he stopped for gas before heading west toward his sister's house in Pensacola.

School districts and multiple universities canceled classes. Airports in Tampa, Tallahassee and Clearwater were closed Thursday, while cancellations were widespread elsewhere in Florida and beyond.

While Helene will likely weaken as it moves inland, damaging winds and heavy rain were expected to extend to the southern Appalachian Mountains, where landslides were possible, forecasters said. Tennessee was among the states expected to get drenched.

Helene had swamped parts of Mexico's Yucatan Peninsula on Wednesday, flooding streets and toppling trees as it passed offshore and brushed the resort city of Cancun. 

In western Cuba, Helene knocked out power to more than 200,000 homes and businesses as it brushed past the island.