"Even though the winds are coming down, the rain threat continues," said James Franklin, a hurricane specialist at the National Hurricane Center. "We expect another 4 to 8 inches, in some of these areas up in north Florida, in particular."
Wakulla, a remote area in northwest Florida known for camping and canoeing, has had more than 26 inches over the past three days, according to the National Weather Service. Several other areas in northern Florida have received more than 10 inches.
The Florida Highway Patrol closed portions of Interstate 10 when troopers reported several areas of flooding on a roughly 50-mile stretch. Authorities warned motorists to use extreme caution on other parts of the highway.
Farther south, four puppies and a young dog drowned when a swollen creek flooded an animal shelter in the city of Starke. Officials placed sandbags and dug trenches outside to protect the shelter, but the water rose quickly Sunday night, The Florida Times-Union reported.
A manatee was found dead in the Tampa Bay area and wildlife crews were trying to rescue two others that had beached nearby. It wasn't immediately clear whether the storm contributed to the animals washing ashore.
Roads were washed out in the area and residents tried to salvage belongings from flooded homes in low-lying areas. At one point Monday, high winds and flooding worries prompted authorities to close two major routes over Tampa Bay into St. Petersburg.
The storm could also bring up to 10 inches of rain to southeastern Georgia.
At least one person was killed Sunday by a tornado spun off by the large storm system.
WFLA-TV reported that a young mother, Heather Town, died Sunday when her Highlands County home was lifted off its foundation and she and her baby girl were thrown into nearby woods. The mother was found clutching the child, who survived.
Alabama authorities searched for a South Carolina man who disappeared in the rough surf.
The bridge leading to St. George Island, a vacation spot along the Panhandle, was closed to everyone except residents, renters and business owners to keep looters out. The island had no power, and palm trees had been blown down, but roads were passable.
"Most true islanders are hanging in there because they know that you may or may not be able to get back to your home when you need to," said David Walker, an island resident having a beer at Eddy Teach's bar. He said he had been through many storms on the island and Debby was on the weaker end of the scale.
Florida Gov. Rick Scott declared a statewide emergency, allowing authorities to put laws against price-gouging into effect and override bureaucratic hurdles to deal with the storm.
A tropical storm warning remained in effect Tuesday morning for about 450 miles of coastline, from Mexico Beach in the Panhandle to Englewood, south of Sarasota.