A stunning 13 million Florida residents were without electricity - two-thirds of the state's residents - as sweltering tropical heat returned across the peninsula following the storm.
But the phenomenon was down to the storm, which combined with low tide, pushed the water away from the bay in what is known as a "reverse storm surge". But by the time Irma arrived in the middle of the night Monday, its winds were down to 100 miles per hour (161 kph) or less. Tornadoes are possible in northeast Florida, and southeastern portions of Georgia and SC through tonight. Forecasters expect it to become a tropical depression on Tuesday.
Officials say Irma's center will move over the western Florida peninsula Monday morning, and further into the southeast USA later Monday evening. It flooded streets and coastal areas, swamped homes, uprooted massive trees, cast boats ashore, snapped power lines and toppled construction cranes.
More people in the USA state of Florida will get to see Tuesday the damage left by Hurricane Irma, while half of the state's population remains without power and roads in many areas are covered by flood waters or debris.
Over in Florida's neighboring Peach State, power outages surpassed half a million.
Irma has been blamed for three deaths in Florida, one in Georgia, and at least 36 in the Caribbean. The Navy is sending an aircraft carrier to Key West to provide emergency services.
Monroe County Administrator Roman Gastesi says relief will arrive on a C-130 military plane Monday morning at the Key West International Airport. Officials closed major bridges. Meanwhile, heavy equipment was seen moving to clear road debris in Florida as chain saws whirred and cleanup crews fanned out. The storm should remain unsafe until Wednesday when it moves into Western Tennessee as a tropical depression.
The U.S. House of Representatives canceled votes scheduled for Monday because of the hurricane.
A Miami roof got ripped off because of the winds.
On Monday, Sept. 4, Irma's sustained winds were 120 miles per hour.
The National Hurricane Center downgraded the storm from a hurricane to tropical storm Monday morning as it reached the northern parts of the state.