Catastrophic Flooding Throughout South Carolina

South Carolina is enduring its worst rains "in 1,000 years," Gov. Nikki Haley said Sunday, urging residents to stay off the roads as conditions were "changing by the minute," with roads flooding and rivers at their highest levels in decades.

According to the National Weather Service, one area of downtown Columbia, the South Carolina capital, received nearly 17 inches of rain in 17 hours, and it was still raining.

"We're in the middle of it," she said. "We've still got easily another 24 hours that you should be extremely careful. We've got more rainfall that's expected."

South Carolina officials had advised residents to not drive any time Sunday or Monday, citing dangers including downed power lines and bacteria in the water.

"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," Haley said.

There were six weather-related fatalities in South Carolina and one-weather related one in North Carolina, according to South Carolina Emergency Management Division as of early Monday morning, bringing the total of seven deaths across the two states.

The South Carolina Department of Transportation earlier announced Sunday that one of its workers died in flood waters in Columbia.

Columbia's police department announced that authorities will commence concentrated search and rescue operations Monday morning. The operation includes helping residents of Columbia and Richland County residents who need to be evacuated. Those citizens who are rescued will be taken out of the flood zone in military vehicles and transported by bus to a designated safe zone shelter, said the department. Crews will also mark a bright orange 'X' on the front door of a house that had been checked.

The National Weather Service Charleston South Carolina tweeted that the flash flood warning for Berkeley, Charleston, and Dorchester counties was extended until 9:30 Monday morning.

South Carolina Emergency Management also reported that 10 counties or municipalities have declared states of emergency, while eight counties or municipalities have imposed overnight curfews.

Some 30,000 customers were without power, and a 75-mile stretch of I-95 was closed as a result of the flooding.

Many residents of Columbia were without drinking water Sunday evening because of water main breaks from the flooding, and officials say those affected should be prepared to be without potable water from the city system for three to four days. Earlier, the city issued a boil water advisory for all of its 375,000 customers

The Coast Guard joined rescue efforts Sunday near Charleston, as rain continued to fall on the area, part of a storm system causing flash flood emergencies and power outages along the East Coast.

The Coast Guard Charleston Sector said it was assisting with land rescues in Berkeley County, near Huger, which is north of Charleston.

The National Weather Service's Charleston South Carolina Forecast Office said that Charleston received 11.5 inches of rain on Saturday, making it the wettest day on record for the city.

Over the next two days, parts of eastern South Carolina and North Carolina could receive 10 more inches of rain.

Other sections of South Carolina experienced incredible amounts of rain. Columbia received over 7 inches Saturday night, while North Myrtle Beach accumulated more than 15 inches worth of water in the past few days.

South Carolina's Greenville-Spartanburg Airport got 2.3 inches of rain Saturday, breaking the record of 0.77 inches back in 1961, according to NWS meteorologist John Tomko.

A flash flood emergency was issued for Berkeley and Charleston counties, with catastrophic flash flooding expected, according to NWS. A flash flood emergency was also issued for southern portions of Dorchester County, the NWS tweeted, which was characterized as a "life-threatening situation."

Meanwhile, Charleston County Emergency Management reported swift water rescues taking place in Charleston, North Charleston, Ladson, Cainhoy and Awendaw, with evacuations continuing in Shadowmoss.

Mario Formisano, emergency management director for Dorchester County, said that the flooding has been widespread and that there were about 140 rescues Saturday evening into Sunday morning. He added that SUVs and trucks were being used to rescue trapped residents, and that those rescued or evacuated were taken to Summerville High School.

According to the South Carolina Emergency Management Division early Sunday morning, more than 29,000 electric customers were without power throughout the state. It also reported that there are 83 road closures across South Carolina, 46 of them in Charleston County.

In downtown Charleston Saturday, roads were closed to incoming traffic as rain flooded roads and left some drivers stranded as their vehicles were surrounded by water. Meanwhile, inland parts of South Carolina were also hit hard by the rain.

The mid-Atlantic region was also affected by flooded roads and power outages were reported in several states.

In response to the storm, President Obama declared a state of emergency in South Carolina, which will bring federal assistance to state and local efforts.

Rachel Katz, Will Gretsky, Matthew Foster, and The Associated Press contributed to this report.