"In all other counties, each state and local agency head is authorized to make closure determinations based on local weather conditions", she said in a memorandum.
Florida was already running short on fuel because of refinery shutdowns from Hurricane Harvey in Texas and Louisiana.
Cities like Jacksonville did suffer flooding, and about 60% of homes across Florida were left without power.
Irma hit South Florida on Sunday with maximum sustained winds of 130 miles per hour, according to the National Hurricane Center. Communications will be non-existent except over hardwired telco equipment (telephone exchanges supply power on the lines and have backup generators), and many people have given up using hardwired phones in their houses. But while millions have been evacuated, two daredevil stormchasers are facing the wrath of Hurricane Irma head-on.
Irma, once ranked as one of the most powerful hurricanes recorded in the Atlantic, hit a wide swath of Florida over the past day, first making landfall on the Florida Keys archipelago and then coming ashore south of Naples and heading up the west coast. Many places including Miami Beach were just beginning to reopen, and highways leading into the state from Georgia had bumper-to-bumper traffic.
Some residents were allowed into the towns of Key Largo, Tavernier and Islamorada on Tuesday morning. Two people were killed in Monroe County, which encompasses the Florida Keys. "As soon as the wind shifts direction, the water will come back quickly and continue to move inland", CNN meteorologist Judson Jones said.
Video from the Keys showed houses shoved from their foundations and boats tossed onto the pavement.
A 55-year-old man died Monday in Tampa, Florida, while using a chainsaw in a tree during storm clean up, the Hillsborough County Sheriff's Office said. There were still more than 100,000 power outages reported in the state Tuesday afternoon.
In Georgia, utilities reported around 1.2 million customers without power Tuesday morning, down from a peak of more than 1.4 million on Monday night.
The Atlanta Journal-Constitution reported at 12 p.m. ET that some 500,000 homes and businesses had lost power in Georgia.
"I've had a lot of calls from nursing homes", Mr. Scott said Tuesday.
Two Florida Power & Light (FPL) plants - Turkey Point and St Lucie - lay in the direct path of the hurricane as it approached the continental United States of America after causing extensive damage in the Caribbean. It could be many weeks before all customers are restored.
- Almost 4 million electric customers are without power across Florida, according to utility companies.
Many homes are without power and rebuilding homes and business will take time. "And now that season for the events and weddings, now it's been highly jeopardized", Crockett said.
"So, usually the eastern side of the storm has winds opposite of the winds aloft, so that's where you have high levels of (vertical) sheer", Ward said.
- At least 26 deaths have been blamed on Irma in the Caribbean islands, where it hit before barreling toward Florida. Associated Press reporters Kim Chandler in Montgomery, Alabama, John Raby in Charleston, West Virginia, and Kate Brumback in Atlanta contributed to this article.