Irma's powerful winds pulled water away from parts of the coast to feed the storm surge in other areas.
Georgia and SC have become the latest USA states to be hit by Hurricane Irma, as the storm weakened to a huge, 415-mile wide tropical depression. At its peak, the wind speed of the hurricane hit almost 300 kilometres an hour.
Officials and forecasters reiterated Saturday that large storm surges along Florida's west coast could cause major flooding.
After the Keys, Irma crossed over warm waters and hit the United States mainland near the beach town of Marco Island.
- In Miami-Dade County, police said they arrested 28 people for burglary and looting.
"We will confront any challenge, no matter how strong the winds or high the water".
Authorities warned the water would "rapidly surge back" into shorelines once winds change direction. Five dolphins were moved from the Florida Keys to Central Florida in advance of the storm, but most zoos and the like in the Miami area said they were trying to keep their animals in place and secure from whatever Irma will bring. No injuries have been reported. Almost five million Floridians are without power, according to Florida Power & Light officials.
Almost 7 million people in the Southeast were warned to evacuate, including 6.4 million in Florida alone.
Gusts topping 90 miles per hour whipped Miami on Sunday, knocking out power to more than 750,000 customers in the Miami-Dade area. And at least two construction cranes partially collapsed.
Scott said Florida is a "resilient" state with great people.
It cut power to millions of people and ripped roofs off homes as it hit a wide swath of Florida on Sunday and Monday.
Those who did not evacuate ahead of the storm are in danger, Federal Emergency Management Agency Administrator Brock Long said Saturday.
"The message has been clear - the Keys are going to be impacted, there is no safe area within the Keys, and you put your life in your own hands by not evacuating", he told CNN. Hurricane-force winds extend out 70 miles from the center of the storm and tropical-storm-force winds extend outward up to 195 miles. Some attempted to leave the state and flee north before Irma makes its trip up Florida.
South Carolina Gov. Henry McMaster issued a mandatory evacuation for some barrier islands.
"This is a storm that will kill you if you don't get out of the way", National Hurricane Center meteorologist Dennis Feltgen said. A high school in Homestead, a city in which 90 percent of its residents were without electricity on Monday, lost its roof.