Florida Power & Light, the state's major electricity provider, deployed almost 17,000 workers ahead of the storm to assist with restoration. Fort Lauderale police also said they arrested several looters.
Hurricane Irma raced ashore on Marco Island just before 4 p.m. Sunday, its 120 mile-per-hour winds stacking water on the island and bending trees.
"The threat of catastrophic storm surge flooding is highest along the southwest coast of Florida, where 10 to 15 feet of inundation above ground level is expected", the National Hurricane Centre said.
A day later, it had weakened to a tropical storm, but still brought risky storm surge flooding to Jacksonville.
According to a spokesperson most of the damage is in the gate areas where water leaked in from the jet bridges.
Irma was at one time the most powerful hurricane ever recorded in the open Atlantic with a peak wind speed of 185 miles per hour last week.
The massive storm triggered evacuation orders for 5.6 million people, and made two landfalls Sunday. There are widespread water and power outages, and the Florida Keys Aqueduct Authorities issued a precautionary boil water notice.
On Sunday morning, Tampa Mayor Bob Buckhorn warned residents that they were "about to get punched in the face by this storm".
The fifth fatality was reported in Orange County, which is near Orlando, after a vehicle crash that was deemed related to the hurricane. At least 40 people died.
After Hurricane Irma began pounded northern Cuba, early this morning the storm has been - for the moment- been downgraded to a Category 3. "Virtually the entire state of Georgia is going to be impacted by this hurricane and the storm related to it", said Deal.
Hurricane Irma has battered the Florida Keys, destroying roadways and isolating residents who didn't evacuate the string of islands, prompting one county's emergency management director to call the situation a possible "humanitarian crisis". "The strength and speed of these states' help has been instrumental in our planned response to Irma".
Buckhorn added, "We know we are ground zero for this storm".
"Flooding is occurring across Florida with Hurricane Irma, " the National Weather Service tweeted.