Hurricane Irma has generated more cyclone energy than the first eight named storms of this year's Atlantic hurricane season combined, and is expected to cause a huge devastation in low-lying Caribbean islands and in Florida, the United States, according to reports by the World Meteorological Organization (WMO) and the World Health Organization (WHO) on Tuesday.
The islands of the Florida Keys and western parts of the state bore the brunt of the category-four hurricane.
"As little as six inches of moving water can knock you down", tweeted the state's governor Rick Scott following the downgrade.
The figure represents nearly 60% of the state's electricity users, who were still experiencing power outage as of 9 p.m. EDT Monday, according to the state's Division of Emergency Management. It shut only one of the two reactors at its Turkey Point nuclear plant about 30 miles south of Miami on Saturday, rather than both, because the storm shifted track.
The scope of damage in Florida and neighbouring states paled in comparison with the devastation left by Irma in parts of the Caribbean, where it razed islands and killed almost 40.
Jacksonville - the largest city geographically in the country - is grappling with a record storm surge and will get slammed with severe flash flooding before Irma continues her destructive northward march to Georgia and beyond. Reports say that 10,000 people made a decision to ride out the storm.
Parts of Georgia lost power on Monday as Irma passed.
Irma's size means that hurricane-strength winds can extend up to 60 miles (95 kilometers) from the storm's eye, while winds at tropical-storm strength can reach more than 415 miles (665 km) from Irma's center, the NHC said.
In Antigua and Barbuda, Arthur Nibbs, minister of Barbuda Affairs who was on Barbuda when Irma hit, said it was the worst storm he'd ever seen.
President Donald Trump has declared a state of emergency in Alabama and ordered federal assistance to the state, according to a White House statement on Monday.
And in Alabama, some city school districts including Birmingham, Huntsville and Auburn planned to close Monday and in some cases Tuesday. Three days after Hurricane Irma rumbled through the region, residents are coping with the aftermath.