Northern Florida, the coastal regions of Georgia and South Carolina and parts of North Carolina are bracing for severe rain and catastrophic flooding this week as the Debby storm system moves up and east.

Debby made landfall as a Category 1 hurricane on the Big Bend coast of Florida early Monday, first hitting the small community of Steinhatchee. It damaged homes and businesses, sent floodwaters rising, caused sweeping power outages across the state and Georgia and led to several fatalities. Debby was downgraded to a tropical storm midday Monday.

But experts say the worst is yet to come as the storm system is expected to stall over the Southeast region.

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The storm continues to drift through southern Georgia and eastern South Carolina as of Tuesday after crossing the Florida-Georgia border on Monday evening.

The National Hurricane Center (NHC) has urged both states to prepare for “catastrophic flooding,” in an update on Tuesday morning. Deadly hazards remain in Florida including downed power lines and severe flooding, the NHC added.

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At least five people have been killed by Tropical Storm Debby as it blows through the southeast.

A 64-year-old truck driver died when his vehicle flipped over in Florida amid heavy rain. The driver lost control on Florida’s I-75, local outlet Fox 13 reports.

In Dixie County, Florida, a 38-year-old woman and 12-year-old boy also died when their car crashed into a guardrail on Sunday night, just ahead of Debby making landfall, local outlet WCTV reports.

A 13-year-old boy also died in Fanning Springs, Florida after a tree crashed into his mobile home on Monday morning. That same day, a 19-year-old in Moultrie, Georgia, died on when a tree fell onto his home.

Savannah’s mayor Van Johnson said that he was “terrified” ahead of Georgia’s coastal city bracing for Tropical Storm Debby’s torrential conditions on Monday evening.

“We plan for a once-in-a-century storm, we don’t plan for a once-in-a-millennium type storm, and that’s where we are right now,” Johnson told CNN.

The storm approached the Florida-Georgia border late on Monday evening, and is expected to continue drifting towards coastal Georgia and South Carolina throughout the week before making its way to the Atlantic Ocean.

Tropical Storm Debby is expected to drift offshore Georgia’s coastline later on Tuesday, the National Hurricane said in an 8am ET update.

It is continuing to move northeast in “slow motion” at 6mph, it added. Debby is predicted to drift back inland over South Carolina on Thursday.

A possible tornado allegedly caused cars to flip over and Walmart shopping carts to “fly in the air” in South Carolina.

Moncks Corner Mayor Thomas Hamilton Jr claimed that a tornado struck near Highway 52 in the Berkeley County town early on Tuesday morning.

“We had minor injuries from the glass at Walmart,” he told local news station Live 5 News.

He added that “shopping carts were flying in the air” around one local resident who he said sustained minor injuries.

Hamilton also said that an RV was seen flipped as local fire services and police responded to the scene who are working on so-called hurricane shifts.

Pictures taken by the mayor and obtained by WCBD-TV show two damaged white pick-up trucks – one flipped completely upside down on top of the other.

A new National Weather Service tornado watch warning has been issued for parts of North Carolina and South Carolina on Tuesday morning.

Almost 2 million residents are susceptible to potential tornado exposure including 402 schools and 39 hospitals in an area which stretches from Charleston, SC, to Burgaw, NC, the announcement said.

Half-inch hail stones could also pelt the two states along with gusts of up to 70mph.

The alert is valid until 5pm ET on Tuesday.

Prior to the arrival of Tropical Storm Debby, Florida coordinated with over 17,000 power line repair technicians to be in place once the extreme weather made landfall.

Bryan Griffin, of the governor’s office, shared a photo of the effort.