Debby isn't done: 2 feet of rain and a drenched East Coast in forecast

Debby, now downgraded from a hurricane to a tropical storm, will continue to dump colossal amounts of rainfall across the Southeast and much of the East Coast over the next few days, likely leading to catastrophic flooding in some areas.

Debby drenched northern Florida as it churned toward Georgia and the Carolinas, threatening a week of torrential downpours and flooding. The storm has already been blamed for at least five deaths .

According to AccuWeather, the heaviest swath of rainfall totals of 18-24 inches is expected to occur across far southeast Georgia and southern South Carolina, including around the cities of Savannah and Charleston.

The rain will slowly make its way up the East Coast during the week and will likely reach New England by the weekend, where the NWS in Boston issued this warning Tuesday: "Rises on rivers as well as flash flooding are possible, but an uncertain storm track casts uncertainty on where the heaviest rain falls."

How much rain will fall? By the time Debby dissipates this upcoming weekend, the storm will have dropped upwards of 50 trillion gallons of rain on the eastern United States from Florida to Maine, according to meteorologist Ryan Maue.

Maue says that makes Debby the wettest landfalling hurricane ever, even topping such powerhouse rainmakers as Hurricane Harvey in 2017. That storm dumped more than 27 trillion gallons of rain over Texas, according to the Texas Division of Emergency Management.

Why is there so much rain?

Debby is a "slow-moving storm," said Brian Haines, the meteorologist-in-charge at the National Weather Service in Charleston, South Carolina. This allows the storm to dump huge amounts of rainfall.

The National Hurricane Center said, "The cyclone is situated in an area of weak steering currents." That means the storm has stalled, University of Miami meteorologist Brian McNoldy said on his blog, which "will be responsible for a very significant flooding threat this week."

While some tropical cyclones increase in forward speed as they move north, Debby is crawling along at only 6 mph, as of Tuesday afternoon, the NHC said.

Drought buster in the Mid-Atlantic?

For some in the Mid-Atlantic, Debby’s rain will be "good news," according to the Capital Weather Gang blog, as "drought is extreme over a large portion of Washington’s western suburbs as well as into adjacent parts of West Virginia, Maryland and Pennsylvania."

"It’s often the case that tropical rainstorms end summer droughts and Debby offers that possibility," according to the Capital Weather Gang.

This article originally appeared on USA TODAY: Debby isn't done: 2 feet of rain and a drenched East Coast in forecast