A man walks through storm surge on the flooded road into Horseshoe Beach, Fla., on Monday after Debby made landfall as a Category 1 hurricane. Christopher O’Meara/Associated Press

HORSESHOE BEACH, Fla. — Tropical Storm Debby slammed Florida on Monday with torrential rain and high winds, contributing to at least four deaths in the state and causing flooding before turning menacingly toward the Eastern Seaboard’s low-lying regions and threatened to flood some of America’s most historic Southern cities.

Record-setting rain was expected to cause flash flooding, with up to 30 inches possible in some areas, the National Hurricane Center said. Up to 18 inches was forecast in central and north Florida. A flash flood emergency was issued into Monday evening for the Lake City area, where up to a foot of rain had fallen and more was expected.

The potential for high water also threatened Savannah, Georgia, and Charleston, South Carolina.

Florida Gov. Ron DeSantis warned that just because the storm was moving into Georgia, it didn’t mean the state wouldn’t continue to see threats as waterways north of the border fill up and flow south.

“It is a very saturating, wet storm,” he said during an afternoon briefing at the state’s emergency operations center. “When they crest and the water that’s going to come down from Georgia, it’s just something that we’re going to be on alert for not just throughout today, but for the next week.”

Debby made landfall along the Gulf Coast of Florida early Monday as a Category 1 hurricane. It since has weakened to a tropical storm and is moving slowly, covering roads with water and contributing to at least five deaths.

A truck driver died on Interstate 75 in the Tampa area after he lost control of his tractor-trailer, which flipped over a concrete wall and dangled over the edge before the cab dropped into the water below. Sheriff’s office divers located the driver, a 64-year-old man from Mississippi, in the cab 40 feet below the surface, according to the Florida Highway Patrol.

A 13-year-old boy died Monday morning after a tree fell on a mobile home southwest of Gainesville, according to the Levy County Sheriff’s Office.

And in Dixie County, just east of where the storm made landfall, a 38-year-old woman and a 12-year-old boy died in a car crash on wet roads Sunday night. The Florida Highway Patrol said a 14-year-old boy who was a passenger was hospitalized with serious injuries.

This National Oceanic and Atmospheric Administration satellite image taken at 11:11 p.m. Sunday shows Hurricane Debby approaching Florida. NOAA via AP

In southern Georgia, a 19-year-old man died Monday afternoon when a large tree fell onto a porch at a home in Moultrie, The Atlanta Journal-Constitution reported.

Nearly 200,000 customers remained without power in Florida and Georgia on Monday afternoon, down from a peak of more than 350,000, according to PowerOutage.us and Georgia Electric Membership Corp.

DeSantis said some 17,000 workers were restoring electricity. He warned residents in affected areas to stay off the roads until conditions are safe.

Airports were also affected. More than 1,600 flights had been canceled nationwide, many of them to and from Florida airports, according to FlightAware.com.

Sarasota, Florida, a beach city popular with tourists, was one of the hardest hit by flooding.

“Essentially we’ve had twice the amount of the rain that was predicted for us to have,” said Sarasota County Fire Chief David Rathbun in a social media update.

Local leaders in Savannah, Georgia, said flooding could happen in areas that don’t usually get high water if Debby stalls out over the city. With winds and rainfall expected to worsen overnight, authorities issued a curfew from 10 p.m. Monday until 6 a.m. Tuesday.

“This type of rain hovering over us, coming with the intensity that they tell us it is coming, it’s going to catch a whole lot of people by surprise,” said Chatham County Chairman Chester Ellis.

In South Carolina, Charleston County Interim Emergency Director Ben Webster called Debby a “historic and potentially unprecedented event” three times in a 90-second briefing Monday morning.

The city of Charleston has an emergency plan in place that includes sandbags for residents, opening parking garages so residents can park their cars above floodwaters and an online mapping system that shows which roads are closed due to flooding. Officials announced a curfew for the city starting at 11 p.m. as some of the heaviest rain is expected to fall overnight.

North Carolina is also under a state of emergency after Gov. Roy Cooper declared it in an executive order signed Monday. Several areas along the state’s coastline are prone to flooding, such as Wilmington and the Outer Banks, according to the North Carolina Floodplain Mapping Program.

North Carolina and South Carolina have dealt with three catastrophic floods from tropical systems in the past nine years, all causing more than $1 billion in damage.

A driver negotiates a flooded street as Tropical Storm Debby passes just to the west of the Tampa Bay, Fla., region on Sunday. Max Chesnes/Tampa Bay Times via AP

In 2015, rainfall fed by moisture as Hurricane Joaquin passed well offshore caused massive flooding. In 2016, flooding from Hurricane Matthew caused 24 deaths in the two states and rivers set record crests. Those records were broken in 2018 with Hurricane Florence, which set rainfall records in both Carolinas, flooded many of the same places and was responsible for 42 deaths in North Carolina and nine in South Carolina.

President Joe Biden was briefed on Debby’s progress while at his home in Wilmington, Delaware, the White House said. Biden approved a request from South Carolina’s governor for an emergency declaration, following his earlier approval of a similar request from Florida. Georgia Gov. Brian Kemp said he has asked Biden to issue a preemptive federal emergency declaration to speed the flow of federal aid to the state.

Vice President Kamala Harris has postponed a scheduled trip to Georgia. Harris’ campaign said her stop planned in Savannah, Georgia, on Thursday, was being put off due to the storm.

Debby made landfall near Steinhatchee, a tiny community in northern Florida of less than 1,000 residents. It’s not far from where Hurricane Idalia made landfall less than a year ago as a Category 3 storm.

Sue Chewning lives in Steinhatchee and weathered both storms. In her nearly 73 years of living in the area, she said she doesn’t recall any direct hits from a hurricane – until this one-two punch from Idalia and Debby.

“Some people may say, ‘I can’t take this anymore’. But I think for the most part … it’s a close-knit community and most of the local people, they’re going to stay, dig down, help each other,” Chewning said.

Martin reported from Atlanta. AP journalists Freida Frisaro in Fort Lauderdale, Florida; Kate Payne in Tallahassee, Florida; Michael Schneider in Orlando, Florida; Russ Bynum in Savannah, Georgia; Jeffrey Collins in Columbia, South Carolina; and Darlene Superville and Will Weissert in Washington, contributed to this report.