The deadly hurricane hit Florida's Marco Island at 3:35 p.m. local time (19:35 UTC) on Sunday with winds gusting at 130 miles (209 kilometers) per hour, according to the National Hurricane Center.

Earlier, 6 million residents of the so-called Sunshine State were ordered to evacuate as Irma threatened violent winds powerful enough to rip boats from their moorings, down power lines and flatten palm trees. 

Shortly after the storm's powerful eye passed over Marco Island, forecasters downgraded Irma to a Category 2 hurricane as it blew through the city of Naples. Forecasters also said "life threatening" storm surges are expected after the eye passes.

Water levels in Naples rose 7 feet (2.1 meters) in less than two hours as the eye of the storm continued moving north. It is expected to hit the heavily populated cities of Tampa and St. Petersburg early Monday morning.

The National Hurricane Center said that although Irma is weakening, the storm is "expected to remain a hurricane at least through Monday morning" as it moves along Florida's west coast. Irma is expected to weaken to a tropical storm as it pushes inland over northern Florida and southwestern Georgia by Monday afternoon, forecasters said.

Hurricane Irma's powerful winds also prompted tornado warnings across Florida, including in Brevard County, which is home to NASA's Cape Canaveral.

The storm led to power outages throughout the state, with Florida Power & Light reporting that over 3.3 million homes and businesses have been affected. Nearly 1 million of those customers are located in Miami-Dade County. There are around 7 million residential customers in the state.

Throughout the state, several airports were closed, including Miami and Orlando International airports.

Read more: Hurricane Irma lashes Florida

Flooding in Miami

Irma threatens to bring dangerous storm surges of up to 15 feet in some areas of the state.

Images from Miami show portions of the city are under water, with reports of several tower cranes collapsing on buildings that were under construction.

Curfews were imposed in Miami, Tampa, Fort Lauderdale and other cities in southern Florida, with some arrests reported for those who broke curfew.

Earlier on Sunday, the storm struck the lower Florida Keys, where a storm surge of over 10 feet was recorded. The state had issued a mandatory evacuation order for over 6 million people in southern and western Florida, making it one of the largest evacuations in US history.

US President Donald Trump told reporters on Sunday that he intends to visit Florida soon after Hurricane Irma passes and praised emergency officials for their work to protect residents.

Trump also approved Florida's request for emergency federal aid to help rebuild once Irma passes through.

"The bad news is that this is some big monster," he said, adding: "Right now, we are worried about lives, not cost."

Stranded wildlife

Irma's strong winds have also caused water to be drawn out of certain bay areas in Florida, leaving some of the state's wildlife stranded.

Locals in Sarasota Bay mobilized to help two manatees that had been stranded by receding waters in the bay. Several people posted photos and videos of the animals in the hope that wildlife officials would respond.

A Facebook user named Marcelo Clavijo later posted on the social media platform that a group of people loaded the manatees onto tarps and were able to drag them into deeper water.

Cuba, Caribbean picking up the pieces

Hurricane Irma killed at least 20 people in the Caribbean and left dozens more injured across several island nations in the Atlantic Ocean.

Read more: Hurricane Irma thrashes Caribbean as Jose strengthens in wake

More than a million people were evacuated in Cuba, where the storm caused significant damage and waves up to 9 meters high were reported, with widespread flooding. Winds were so intense they reportedly damaged the gauge used to measure them.

State media reported that people took shelter in tunnels, caves and official emergency shelters.

The Bahamas had a close call, but ultimately escaped the worst of Irma's destructive wrath, with no casualties or major infrastructure damages reported.

Jose hovering in Atlantic

The Category 3 hurricane Jose followed part of Irma's track in the Caribbean, but ended up sparing the islands of St. Martin and St. Barts, which had already suffered massive damage from Irma.

St. Martin, which is divided between France and the Netherlands, saw around 70 percent of the infrastructure destroyed on the Dutch side following Hurricane Irma, officials said. Dutch Prime Minister Mark Rutte said "no new damage" had been caused by Hurricane Jose.

The National Hurricane Center said in a statement that Hurricane Jose "will remain well to the east of the Bahamas" over the next couple of days and is not expected to pose a threat to the United States.

rs,mm/jm (AP, AFP, dpa, Reuters)