Authorities in Columbia told all 375,000 of its water customers to boil water before drinking because of water line breaks and the threat of rising water to a treatment plant.
Among the rescued were 90 people — including several elderly people and dozens of pets — who were forced to evacuate their homes in Irmo, 10 miles northwest of Columbia, NBC station WIS reported.
Local fire officials said the Irmo flooding was due to the rainfall, as well as the decision to open a nearby dam in an attempt to control rising water levels.
"We didn't get the word that they were going to open the dam until 7 p.m. [Sunday] on the news," local resident Cindie Denning told WIS. "Nobody told us."
The all-time state record for the most rain in 24 hours was 14.80 inches, set during Hurricane Floyd in 1999. This was broken in several places over the weekend, with gauges registering 21.66 inches of rain falling in Dalzell, 30 miles east of Columbia, as of 9:46 p.m. Sunday, according to The Weather Channel.
Experts said parts of South Carolina experienced a "1000 year flood event," meaning in any given year there is a 1-in-1000 chance of observing such rainfall totals.
Myrtle Beach was "ground zero" for the storm Monday, with the heaviest rain expected there, although the precipitation could move through Charleston before heading out to sea, Weather Channel lead meteorologist Kevin Roth said.