Even as glimmers of hope emerged from parts of the state forecasters once anxious would be razed by the storm, the fate of the Florida Keys, where Irma rumbled through with Category 4 muscle, remained largely a question mark.
The storm has weakened to a tropical depression, but was still dropping heavy rains in parts of North Carolina, South Carolina, Georgia, Alabama, Mississippi, Tennessee and Kentucky on Tuesday.
The warning comes in the aftermath of Hurricane Irma, the strongest ever Atlantic Ocean hurricane on record, which left a terrifying path of destruction behind it as it moved across the Caribbean and towards the United States, killing at least 22 and injuring hundreds more.
In Miami-Dade County, where roads flooded and debris flew, around three-quarters of residents (820,000 out of 1.1 million) are without power as of Monday.
But forecasters have warned the threat to life still remains, as Florida continues to be battered by 100mph winds and torrential rain.
A woman in Georgia died when a tree fell on a vehicle in a private driveway, according to the website of the Forsyth County Sheriff's Office. He said nearly every mobile home park in the Keys had overturned homes.
"This is likely to be one of the largest and most complex power restoration efforts in US history", said Tom Kuhn, president of the Edison Electric Institute, an industry trade group.
Sewa International, one of the Indian-American organisations carrying out relief and rescue work, provided shelter to more than 300 families in the homes of its volunteers and members in and around Atlanta.
Around the Tampa-St. Petersburg area, where Irma rolled through early Monday, damage appeared modest.
The hurricane made a landfall in lower Florida Keys just before 9 am (local time) with wind gusting 130 miles per hour.
However, Irma is expected to fizzle out over land while Hurricane Jose will make a loop before moving west again.
Florida's coastal and southern areas have been evacuated since last week with a record 6.3 million people leaving their homes.
Some 166,000 people in Georgia, including more than 17,000 in the city of Savannah, lost power as the outer bands of the storm lashed the state.
By Monday morning at 8 a.m., Hurricane Irma is forecast to be nearing Gainesville in central-northern Florida.
At least 40 people were killed after Irma's destructive trek across the Caribbean and the U.S.