MIAMI United States (AFP) – At least four people were killed as Tropical Storm Debby swept over Florida on Monday, threatening southeastern US states with record-breaking rainfall and potentially catastrophic flooding.

A 13-year-old boy died when a tree was blown onto a mobile home in Levy County, the sheriff’s office there said, after Debby made landfall on Florida’s Gulf Coast earlier in the day as a Category One hurricane.

The Hillsborough County Sheriff’s Office said it had pulled out a semi-truck along with its deceased driver after it toppled into a bypass canal off I-75, while a 38-year-old woman and 12-year-old boy from Crawfordville were killed during a crash in bad weather on Sunday night, the Florida Highway Patrol said.

A 14-year-old boy survived the crash with serious injuries.

Authorities say the danger remains high as the storm moves over the state and into Georgia and South Carolina, despite the downgrade by the National Hurricane Center (NHC) from hurricane back down to tropical storm.

“This is a level four out of four risk for excessive rainfall,” Michael Brennan, director of the NHC, told reporters.

“This is going to result in a prolonged extreme rainfall event with potential for catastrophic flooding across coastal portions of Georgia, South Carolina, even extending up into North Carolina,” he added.

Florida Governor Ron DeSantis also warned of “significant” flooding over the coming days, and said the state had already seen storm surge and some water rising.

Around 275,000 customers in Florida and Georgia have lost electricity so far, according to tracker poweroutage.us.

“We have a lot of restoration personnel ready to go to get it back on,” DeSantis said.

The NHC warned of life-threatening storm surges along the Gulf coast, with up to five feet (1.5 meters) of inundation above ground level in some areas.

By early afternoon, the storm was packing maximum sustained winds of 65 mph (100 kph) as it swept over northern Florida. Storm surge warnings are in effect in parts of the three states, indicating “life-threatening inundation, from rising water moving inland from the coastline.”

The storm will probably cause catastrophic flooding with “potentially historic heavy rainfall” when Debby moves northeast across Georgia and South Carolina over the next few days, the NHC said.

But it said Debby was weakening. The storm’s maximum sustained winds were 80 miles (130 kilometers) per hour at landfall but dropped to 65 mph at the 2:00 pm ET (1800 GMT) update.

Debby is expected to dump up to 18 inches of rainfall in parts of Florida, and as much as 30 inches in coastal Georgia, South Carolina, and parts of North Carolina before the week is over, the NHC said.

Mandatory evacuations were ordered for part of Citrus County, Florida, with eight other counties under voluntary evacuation orders, local media reported.

The governors of Georgia and South Carolina declared a state of emergency ahead of the storm’s arrival.

President Joe Biden on Sunday approved an emergency declaration for Florida, allowing federal aid to be expedited.

DeSantis has activated the state’s National Guard, with 3,000 service members on standby to help with storm response.

Meanwhile in the Florida Keys, Debby washed ashore 25 tightly wrapped packages of cocaine worth more than $1 million, according to a post on X by US Border Patrol acting chief patrol Agent Samuel Briggs II.