The hurricane which killed at least 22 people in the Caribbean, was considered a life-threatening danger to Florida, and could inflict a natural disaster causing billions of dollars in damage to the third-most-populous USA state.
Irma's eye was due to strike the Florida Keys on Sunday morning before driving up the state's southwestern coast Sunday afternoon, according to the hurricane center.
Hurricanes are large swirling storms, characterised by winds that can go up to 119 kilometers per hour (74 mph) or higher.
South Florida's large population of elderly residents posed a severe test for the emergency shelters, many of which were not equipped for people with elaborate medical needs.
Hurricane Irma has regained strength as it begins pummeling Florida, threatening nearly the entire southeastern U.S. state after leaving a deadly path of destruction across the Caribbean islands.
Still, many Cubans expressed a sense of relief after the eye of the first Category 5 storm to make landfall on the island since 1932 passed over the northern keys, just grazing the mainland with its full force.
The National Weather Service in Atlanta, Georgia, has issued a tropical storm watch for the area Monday and Tuesday and schools throughout Georgia, including the University of Georgia, planned to close Monday.
Storm surges pushed by a high tide were forecast to be as high as 4.6m for low- lying area along the state's west coast on Sunday, which could produce catastrophic flooding for thousands of homes.
US President Donald Trump said his administration is monitoring the situation around the clock and is "as prepared as we can be". When Irma arrives, the Times reported, it will likely bring high winds, heavy rain and possibly tornadoes to the area.
The clean-up has now begun in Cuba, as the deadly storm heads on to the US.
Here's all the ways Hurricane Irma could impact Florida's businesses and economy.
The almost 400-mile-wide storm is expected to make a slow, ruinous march up Florida's west coast, straight toward the heavily populated Tampa-St.
With sustained winds at 120 miles per hour, Irma slowly began turning from Cuba's northern coast up into the Florida Strait on Saturday, the National Hurricane Center said.
At least 30 deaths are attributable to the storm, including three in Florida.
The live stream at Key West has proved a big hit online, and this is one of the reasons why.
Laurie Mastropaolo said she weathered Sandy and other storms on Long Island, and was not convinced she had to leave.
Storm surge of 4-6 feet above ground may happen beginning Sunday evening, the Weather Service said.
"As Irma's track continues to evolve, we are adjusting our crews and moving them in position as we need to so they're best able to respond", he said.
With Fema still dealing with the aftermath of Hurricane Harvey in Houston, Irma could test the agency's ability to handle two disasters at the same time.
In downtown Miami, two of the two dozen construction cranes looming over the skyline collapsed in the wind.
The US government said it was sending aircraft to evacuate citizens from one of the hardest hit islands, St Martin.
Tamara Huggins, one of the city's diaspora from Antigua and Barbuda, told CBC News Saturday her family was on the once-lush Caribbean island when the historic hurricane hit.