Most of the Sunshine State appeared to have dodged forecasts of catastrophic damage despite dire early warnings.
But Irma's overall death toll jumped to at least 40 after Cuba reported that 10 people had been killed there over the weekend.
Irma roared ashore as a powerful Category 4 hurricane when it hit the far southern Florida Keys on Sunday, tearing boats from their moorings, uprooting palm trees and downing power lines, after devastating a string of Caribbean islands.
Across the Caribbean, hard-hit island residents struggled to get back on their feet as Britain, France, the Netherlands and the United States increased relief efforts.
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French President Emmanuel Macron traveled to the region Tuesday to tour devastated French territories, joining the Dutch king who had arrived in his country's Caribbean territories on Sunday.
In Florida, the damage in most cases were not as bad as feared.
"If this had been a Category 4 hurricane the whole scenario would have been completely different," said Bob Lutz, a 62-year-old business owner.
"It's horrible what we saw," Scott said after flying over the island chain aboard a Coast Guard helicopter.
He said the water, electricity and sewage systems in the Keys were non-operational, and that trailer parks had been "overturned."
"We now go through the much longer phase, which is the recovery phase," said Miami Mayor Carlos Gimenez. "And believe me, folks, some of this is going to take a while, especially power restoration."
Most Keys residents evacuated from the low-lying tourist archipelago, known for its fishing, scuba diving and boating, before Irma struck.
Authorities were allowing residents and business owners in the upper part of the Keys to begin returning on Tuesday.
"Returning residents should consider that there are limited services. Most areas are still without power and water. Cell service is spotty. And most gas stations are still closed," Monroe County authorities said in a Facebook post.
The National Hurricane Center downgraded Irma to a tropical depression in its 0300 GMT Tuesday bulletin.
Irma's maximum sustained winds dropped to 35 miles (56 kilometers) per hour, and the storm's eye was in western Georgia, and expected to cross into eastern Alabama and Tennessee later Tuesday.