Extreme winds and storm surges continued in the Lower Florida Keys area, which includes Key West.
With sustained winds of up to 60 mph, Irma had crossed into Georgia and was situated about 47 miles northeast of the Florida state capital Tallahassee, the National Hurricane Center said at 11 a.m. ET.
Irma, now a Category 1 storm and forecast to weaken into a tropical storm as it moves over northern Florida and Georgia, threatens to sap natural gas demand by cutting use from power plants.
- About 6.5 million electric customers are without power in Florida, according to Floridadisaster.org. FEMA chief Brock Long has said some places won't have electricity for weeks.
People in the heavily populated Tampa-St.
Tampa has not been struck by a major hurricane since 1921, when its population was about 10,000, Feltgen said.
Irma has been downgraded from a hurricane to a tropical storm, with winds of 70 miles per hour, the National Hurricane Center said.
"The center of Irma will move into southwestern Georgia later today, and move into eastern Alabama Tuesday morning", the National Hurricane Center said.
"We're doing everything possible to help save lives and support those in need", Trump said.
"Stay off the roads, stay off the streets, let us complete our assessment, clear the roads of water, power lines, trees and then you can get out there and determine what happened to your individual property or your neighborhood", said Fort Lauderdale Mayor Jack Seiler. "Driving conditions are going to be bad".
The Ohio State University Geography Department has teamed up with Texas A&M and the University of MI to produce a model that projects power outages caused directly by the impact of hurricane-force wind gusts.
"My heart goes out to the people of the Keys", Scott said after flying over the Keys in a C-130 aircraft. The surge could go as high as 10 feet throughout the Keys. "I'm originally from Miami, and I definitely wanted to see the beach", said one woman.
A tornado damaged homes in east-central Florida's Palm Bay late Sunday morning, the National Weather Service said - while Irma's eye wall was spinning off the Everglades, more than 150 miles to the southwest.
More than 200,000 people waited in shelters across Florida. Parts of coastal Georgia and SC were under a storm surge warning. Tampa's storm surge could be between five and eight feet. At midday Saturday, the plywood sheets and metal window shutters so ubiquitous in South Florida were still comparatively rare in St. Petersburg. The surge also caused flooding to break Dora's record in downtown Jacksonville, the weather service said.
Irma pounded Naples and Marco Island before heading to Tampa. Water levels were up throughout the day, rising almost a foot above normal in Key West after 4:30 p.m. and more than a foot near Vaca Key.
Given its mammoth size and strength and its projected course, it could still prove one of the most devastating hurricanes ever to hit Florida and inflict damage on a scale not seen in the area in 25 years.
In nearby Clay County, crews pulled at least 46 people from flooded homes, and still more were stranded, said emergency operations manager Joe Ward.
As Irma began moving into Georgia, a tornado spun off by the storm was reported on the coast, and firefighters inland had to rescue several people after trees fell on their homes.
But not much news has emerged since Irma reached Cuba.
Trump stressed that his top priorities are life-saving and life-sustaining efforts in affected areas, the White House said.