CHARLESTON, S.C. (NewsNation) — Tropical Storm Debby has claimed five lives and led to the rescue of 500 others from flooded homes as Northern Florida, the coastal regions of Georgia and South Carolina and parts of North Carolina brace for severe weather.

The National Hurricane Center warned of “life-threatening flash flooding and major river flooding,” as the slow-moving storm brings torrential rains.

More than 140,000 people are without power across the Southeast. The heaviest rain is expected early in the week, but it could continue through Saturday, forecasters said.

Debby made landfall as a Category 1 hurricane on Florida’s Big Bend on Monday, hitting the small community of Steinhatchee first. It damaged homes and businesses and caused flooding before being downgraded to a tropical storm later that day.

‘I don’t believe this storm is done’: Gov. Brian Kemp

On Tuesday, Georgia Gov. Brian Kemp urged residents to stay home if they can and remain patient as crews work to clear roads and restore power.

He added that forecasters expect areas within 50 to 70 miles of Savannah, specifically Chatham County, Effingham County and Screven County, to continue to be impacted by Debby. He added that forecasters expect an additional 4-5 inches to hit the state and in the worst-case scenario, up to 8 inches of rain.

“Unfortunately, I don’t believe this storm is done with us yet,” Kemp said Tuesday during a news conference. “We know that this is gonna come back and we’ll be prepared for that. But, I just want to make sure our citizens understand that this event is not over.”

President Joe Biden approved an emergency declaration for much of Georgia, making disaster assistance available for the effects of Hurricane Debby, the Federal Emergency Management Agency said Tuesday.

The declaration authorizes FEMA to mobilize equipment and other resources to protect lives, property and public health, including coordinating evacuations and shelters.

Tropical Storm Debby-related deaths

The death toll from Debby has risen to five.

In Florida, a 13-year-old boy was killed when a tree fell onto a mobile home in Levy County, near Gainesville, NewsNation affiliate WKRN reported.

In Hillsborough County, near Tampa, a driver was found dead after his semitrailer became submerged in the Tampa Bypass Canal off Interstate 75 during the storm Monday.

In Dixie County, just west of Gainesville, officials reported that a 38-year-old woman and a 12-year-old died when their car crashed into a guardrail on U.S. Highway 19 on Sunday night.

In southern Georgia, a 19-year-old was killed after a large tree fell onto a porch at a home in Moultrie, The Moultrie Observer reported.

How much rain is expected?

Forecasters predict the system could bring up to 20 inches of rain to widespread areas of the Southeast, with some areas getting up to 30 inches.

That would be a record-setting rainfall, shattering the record from a tropical system in 2018’s Hurricane Florence. More than 23 inches of rain was recorded in South Carolina after that storm hit the Carolinas.

Although Debby was classified as a Category 1, “It really is worthy of a Category 3 or 4 rating, if you want to talk about rainfall impacts,” said Jeff Masters, founder of Weather Underground, now with Yale Climate Connections. “That’s going to cause a lot of damage.”

What areas are at risk?

Northern Florida and low-lying areas including Savannah, Georgia, and Hilton Head Island and Charleston, South Carolina, are expected to see the most severe flooding. North Carolina could also be impacted.

Officials in Savannah warned the area could see a month’s worth of rain in four days if the system stalls. There were also flooding concerns for Tybee Island, Georgia’s largest public beach 18 miles east of Savannah. On top of any torrential downpours that Debby dishes out, the island could get even wetter from 2 to 4 feet of storm surge, according to the National Hurricane Center.

“We don’t know how much rain is going to fall, but we have to prepare for the worst,” Hilton Head Island Mayor Alan Perry said on a video posted to Facebook. “If that happens, we will see an event we have never seen on Hilton Head before.”

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

Few places in South Carolina are as susceptible to flooding as Charleston. Much of the city and surrounding areas founded in 1670 were built on land created by using fill dirt and other debris. Rising sea levels cause a number of minor flooding events even without a storm and like many coastal cities, Charleston can’t drain well.

The city doesn’t expect a massive amount of flooding from the ocean, but the storm is still dangerous. Heavy rain can back up into the city, also causing flooding.

The Associated Press contributed to this report.