Hurricane Idalia slammed into northwest Florida as an "extremely dangerous" Category 3 storm early Wednesday, as officials warned of catastrophic impacts including storm surges of up to 16 feet (about five meters).

Authorities in the southern US state described Idalia and its potentially deadly high surging waters as a once-in-a-lifetime event for Florida's northwest coast, ordering mass evacuations and issuing flood alerts.

The US National Hurricane Center (NHC) said Idalia, which earlier raked western Cuba, was packing maximum sustained winds of approximately 125 miles (215 kilometers) per hour as it made landfall around 7:45 am (1145 GMT) in Florida's marshy Big Bend area.

Unlike most other coastal regions in the state, Big Bend, located along the arch of the Gulf of Mexico, does not have barrier islands.

"This thing is powerful, if you're inside, just hunker down until it gets past you," DeSantis told a press conference just before landfall.

More than 140,000 customers in Florida were without electricity as of 8:00 am, according to tracking website PowerOutage.us.

"Extremely dangerous Category 3 Hurricane Idalia makes landfall in the Florida Big Bind," the NHC said, noting that the eye made landfall near the community of Keaton Beach.

It warned of a possible disastrous storm surge of 12 to 16 feet in some coastal areas.

"Water levels along the coast of the Florida Big Bend are rising rapidly," it warned, noting that at Cedar Key, a string of islands jutting into the Gulf, approximate inundation was at nearly six feet.

"While Idalia should weaken after landfall, it is likely to still be a hurricane while moving across southern Georgia, and near the coast of Georgia or southern South Carolina late today," the NHC said.

- 'Time to shelter in place' -

"Very few people can survive being in the path of a major storm surge, and this storm will be deadly if we don't get out of harm's way and take it seriously," said Federal Emergency Management Agency (FEMA) chief Deanne Criswell.

In the small coastal town of Steinhatchee on Tuesday, resident Robert Bryant made final preparations to evacuate inland with his two cats and a dog.

"Hopefully, it just blows over and we have a bit of wind... but you prepare for the worst and hope for the best," the 18-year-old student told AFP.

Another Steinhatchee resident, 71-year-old John Paul Nohelj, told AFP he would stay put.

"If you live near the water, you're gonna get a wet butt once in a while," he said, downplaying the risk.

The nearby cities of Tampa and Saint Petersburg, part of a metropolitan area that is home to more than three million people, are of particular concern, authorities said.

"There's a danger of life-threatening storm surge along portions of the Florida Gulf Coast from Tampa Bay to the Big Bend region," said Matthew Payne of FEMA's Office of Response and Recovery.

"The time to evacuate has come and gone. It is time to shelter in place," Tallahassee Mayor John Dailey said Wednesday on NBC's "Today" show.

- Airports, ports closed -

DeSantis had urged residents of 23 counties along Florida's Gulf coast to evacuate and head to shelters or hotels outside the danger zones.

The US presidential candidate said the hurricane was on track to be the strongest to impact the region in more than a century.

Meteorologists are also pointing to a rare blue supermoon which could further raise tides above normal levels just as Idalia pounds the coastline.

Almost 150 people were killed last year when Hurricane Ian slammed Florida's west coast as a Category 4 storm, bringing ocean surges and strong winds that downed bridges and swept away buildings.

The storm is forecast to dump up to 12 inches (30 centimeters) of rain in parts of Florida, Georgia and South Carolina, according to the NHC.

Tampa International Airport and other regional airports closed ahead of Idalia's arrival, while flights were disrupted along the US East Coast as another hurricane, Franklin, churns in the Atlantic.

Several Florida ports were closed to vessel traffic as of Tuesday night, according to the US Coast Guard.

- 'Marine heat wave' -

In Cuba, the storm flooded several communities including parts of the capital Havana and knocked out power to about 200,000 people but there were no deaths reported.

The storm then moved out over the Gulf of Mexico, which scientists say is experiencing a "marine heat wave" -- energizing Idalia's winds as it raced towards Florida.

Scientists have warned that storms are becoming more powerful as the world warms due to climate change.