COLUMBIA, S.C. (AP) -- Hundreds were rescued from fast-moving floodwaters Sunday in South Carolina as days of driving rain hit a dangerous crescendo that buckled buildings and roads, closed a major East Coast interstate route and threatened the drinking water supply for the capital city.
The powerful rainstorm dumped more than a foot of rain overnight on Columbia, swamping hundreds of businesses and homes. Emergency workers waded into waist-deep water to help people trapped in cars, dozens of boats fanned out to rescue others in flooded neighborhoods and some were plucked from rooftops by helicopters.
With so much water, officials said it could take weeks or even months to assess every road and bridge that's been closed around the state. Several interstates around Columbia were closed, and so was a 75-mile stretch of Interstate 95 that is a key route connecting Miami to Washington, D.C. and New York.
"This is different than a hurricane because it is water, it is slow moving and it is sitting. We can't just move the water out," Gov. Nikki Haley said at a news conference.
One death was reported in the area on Sunday, bringing weather-related deaths to seven since the storm began days earlier.
The system drenching South Carolina was part of an unusual combination of weather conditions involving a slow-crawling low pressure system meteorologists called unusually deep for this time of year. [...] ****** Wow. For those who look for Signs and Portents, God has gotten very talkative these days. It's not the disaster you're expecting, it's the one that comes in on your blind side and strikes at the same time as the other disaster that's the greatest danger. I could be talking about the refugee crisis hitting Europe or the flood in South Carolina.
But Carolinians are very fortunate -- we're all fortunate here on the East Coast. Hurricane Joaquin didn't make landfall. If that had happened at the same time as the 'weird' weather system hitting the Carolinas, I don't want to think about it.
Yet just as it is, South Carolina is going through a flood that is a "1 in a 1,000 year" statistical event for rainfall levels, as the weatherman in the CNN video explained it.
The good news is that Governor Niki Haley and her crew and all the relevant responders have rallied brilliantly, and Carolinians have showed common sense in avoiding the dangers of flooding; all this has kept the death toll to 3, so far. [The Associated Press reported this afternoon that the toll stands at 7]
But Nature isn't finished partying in that part of the USA and already rivers in the state are at historic highs.
Well, one perk is that the deluge should wipe out the drought that settled into parts of North Carolina.
Charleston, South Carolina (CNN)South Carolina Gov. Nikki Haley didn't mince any words Sunday about just how dangerous a situation the weather had become in her state.
"We haven't seen this level of rain in the Lowcountry in 1,000 years," Haley said at an afternoon press conference. "That's how big this is."
It wasn't hyperbole.
Certain areas of South Carolina had never before been deluged with such eye-popping rainfall tallies: more than 24 inches in Mount Pleasant, nearly 20 inches in areas around Charleston and more than 18 inches in the Gills Creek area of Columbia, according to CNN meteorologist Taylor Ward.
Haley: keep off the roads
Steven Pfaff of the National Weather Service said the "phenomenal amount of rainfall" was "a very dangerous situation."
"Flash flood warnings have been issued and many areas that received a large amount of rainfall 24 hours ago are being hit hard again," said Plaff. "This is an extremely dangerous situation in those areas."
The biggest danger seemed to be on the state's roadways; the historic rainfall and flooding had been responsible for three deaths and more than 750 roadway rescues in one 12-hour stretch, according to Haley.
The weather service issued a public service announcement video reminding people not to drive through rushing waters, no matter how shallow the water appears to be. "Do not attempt to drive into flooded roadways ... it takes just 12 inches of flowing water to carry off a small car. Turn around, don't drown," it said.
"Regardless of where you are in the state, stay home," said the governor. "Stay off the roadways."
But she didn't just urge South Carolinians to stay off the roads. In some places she made sure of it by closing all interstate highways in and around the capital city of Columbia.
"This is an incident we've never dealt with before," she said.
National Guard deployed
Haley announced Sunday that in addition to the eight swift water rescue teams and 11 aircraft, 600 National Guardsmen had been deployed to assist in rescues and evacuations, and that hundreds more were on standby.
The day before, President Barack Obama signed a statewide emergency declaration retroactive to Thursday, authorizing federal aid in anticipation of more rain.
Haley also said several fellow states, including North Carolina, Tennessee and Florida had lent resources as well.
Not over yet
The weather service forecast "catastrophic flash flooding" overnight into Monday in Berkeley County in South Carolina, where more than 18 inches of rain had fallen in 24 hours, according to the CNN Weather Center.
"It's not over," warned Haley. "We are in the middle of it...we have another 24 hours of this."
Northeast on deck
The wet misery isn't just limited to South Carolina; as of Sunday evening, both Carolinas, New Jersey and Virginia were under states of emergency, and the weather service has issued flood watches stretching from Georgia to Delaware.
But Hurricane Joaquin, downgraded to Category 3 strength earlier in the day Sunday and only expected to continue to weaken, isn't necessarily the culprit -- it's coming from two sources.
The low pressure area associated with the rain soaking the Carolinas is funneling heavy tropical moisture into the region, creating the torrential rainfall, the CNN Weather Center said.
The moisture the storm is pulling in is also associated with Hurricane Joaquin, but the two systems shouldn't be confused.
Joaquin inched northward in the Atlantic on Sunday, but luckily away from U.S. shores. However, the storm is expected to push in a storm surge in the Northeast as it passes, resulting in a one-two water punch.
"Life-threatening rip currents, high surf and coastal flooding, mainly at high tides, will stretch nearly the entire eastern U.S. coast," CNN meteorologist Michael Guy said.
CNN's Nick Valencia reported from South Carolina. CNN's Kevin Conlon wrote from Atlanta. CNN's Ben Brumfield, Ashley Fantz, Greg Botelho, Joe Sutton, Devon Sayers, Tony Marco, Shawn Nottingham, Dominique Dodley, Michael Martinez and Kerry Chan-Laddaran also contributed to this report.