By CNN Wire Service.

(CNN) -- This is the kind of deluge that might happen only once every 1,000 years.

South Carolina is grappling with a historic flooding that has led to several deaths, shut down interstates and sent search crews scrambling to rescue those trapped by rising waters.

"This is an incident we've never dealt with before," Gov. Nikki Haley said.

The hardest-hit swath of South Carolina stretches from the capital city of Columbia, right in the middle of the state, all the way to the coast, from Georgetown down to Charleston.

On Sunday, Columbia endured its rainiest day in history Sunday, according to the National Weather Service.

"We are at a 1,000-year level of rain," the governor said. said "That's how big this is."

It wasn't hyperbole.

A "1,000-year rainfall" means that the amount of rainfall in South Carolina has a 1-in-1,000 chance of happening in any given year, CNN meteorologist Taylor Ward said.

At least 600 National Guardsmen, 11 aircraft and eight swift water rescue teams are taking part in search-and-rescue efforts, the governor said Sunday. More than 200 water rescues took place in the state from Saturday night to Sunday afternoon, the state's emergency management agency.

And it's not over yet.

The National Weather Service forecast "catastrophic flash flooding" into Monday in Berkeley County, where more than 18 inches of rain had fallen in 24 hours.

"The problem is rivers are going to continue to rise for several more days," CNN meteorologist Tom Sater said.

'We have lost everything'

Resident Angela Williams watched the relentless rainfall deluge and destroy her neighborhood in Columbia.

"We have lost everything. What I got on my body is what we have," she told CNN affiliate WIS. "Pretty much everybody down that hill there has lost everything ... our vehicles, our clothes, everything.

"But the best thing is that we still have our lives."

At least five people have been killed, including a state transportation employee.

Timothy Wayne Gibson, 45, died Sunday in flood waters while overseeing work in Columbia, the South Carolina Department of Transportation said. Details of the four other weather-related deaths were not immediately available.

On Saturday, President Barack Obama signed a statewide emergency declaration retroactive to Thursday, authorizing federal aid in anticipation of more rain.

The state asked residents to:

Take the day off:

Haley said Sunday she is "heavily encouraging" county offices and schools to close Monday.

"The main reason for that is this is not going to clear up until at least Tuesday or Wednesday," the governor said.

More than 70 miles of Interstate 95 were closed late Sunday as floodwater spilled onto freeway lanes. And parts of all interstates leading out of the capital had to be shut down due to dangerous flooding.

"Regardless of where you are in the state, stay home," the governor said. "Stay off the roadways."

Boil drinking water:

State emergeny officials said Columbia residents should boil their drinking water.

"Rising water from flooding can carry viruses, bacteria, chemicals and other submerged objects picked up as it moves through storm water systems, across industrial sites, yards, roads and parking lots," the South Carolina Emergency Response Team said.

Those who are unsure about whether to boil their water should contact local officials or boil their water as as precaution, it said.

In Columbia, five hospitals could be evacuated due to water shortages, officials said.

Stay indoors:

Richland County Sheriff Leon Lott set a curfew for the county and city of Columbia from Sunday night until 6 a.m. Monday. The curfew will be re-evaluated Monday.

During the darkness of night, "the conditions will become even more dangerous then what we have already experienced throughout the day," the sheriff's department said.

Stay off roads:

The National Weather Service issued a public service announcement video reminding people not to drive through water on streets, no matter how shallow it appears to be.

"Do not attempt to drive into flooded roadways," it said. "It takes just 12 inches of flowing water to carry off a small car. Turn around, don't drown."

CNN's Nick Valencia, Kevin Conlon, Devon Sayers, Tony Marco, Shawn Nottingham, Dominique Dodley and Kerry Chan-Laddaran also contributed to this report.


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