Warnings of risky storm surges remained in effect through vast swaths of peninsular Florida, where more than six million people had been ordered to flee Irma in one of the biggest evacuations in USA history.
Aid rushed in to hurricane-scarred Florida early Tuesday, residents began to dig out, and officials slowly pieced together the scope of Irma's vicious path of destruction across the peninsula.
About 100 workers from Mississippi Power will be among the first crews arriving at the Coliseum, which has become a staging area for teams that will be responding to Hurricane Irma damage.
"What we really fear more than anything is that storm surge", Buckhorn told CNN's Anderson Cooper on Sunday.
Brian Entin, reporter for South Florida TV station WSVN, is in downtown Miami and filmed water rising along one of the city's main streets. That brings the total number asked to evacuate multiple states to almost 7 million.
Traffic on roads around the county was light Saturday morning.
Tampa hasn't been hit by a major hurricane since 1921, but on Sunday it looked like Hurricane Irma was about to change that.
Millions of people were still without power in Florida.
Another 540,000 have been asked to evacuate in the eastern part of Georgia.
Even after the evacuation order was issued, they talked of riding out Irma at home. That includes Hilton Head Island, the most populous of the islands with about 40,000 residents.
The deadly hurricane hit Marco Island at 3:35 p.m. local time (19:35 UTC) on Sunday with winds gusting at 130 miles (209 kilometers) per hour just 15 miles south of Naples, according to the National Hurricane Center.
The center said the storm was beginning to pull away from the Leeward island chain.
Irma, weakened to a tropical depression, is expected to push into Alabama, Mississippi and Tennessee over the next two days.
Areas without water, power or communications are likely to remain so for some time.
A collapsed construction crane is seen in Downtown Miami as Hurricane Irma arrives at south Florida on September 10, 2017.
The two USA agencies have also had their eye on the not-so-far behind Category 4 Hurricane Jose and nearby Category 1 Hurricane Katia, now a tropical depression, in the Gulf of Mexico.
Rubio spoke with AP from the Miami-Dade Emergency Operations Center. Rubio says EPA officials have been assessing the sites for 72 hours. "This storm is the real deal", he said.