Flooding could be life-threatening this weekend, forecasters warned, as a deluge continues through Sunday. That’s without an impact from Hurricane Joaquin, which was expected to stay far offshore.

“The concern is that people are going to be so focused on the hurricane, they won’t realize that this is going to be a significant event,” said meteorologist John Quagliariello, with the National Weather Service, Charleston. “It could be historic. People should be aware of that.”

Tri-county high schools are closed for Friday, along with the College of Charleston, Medical University of South Carolina, The Citadel, Charleston Southern University, Charleston School of Law and Trident Tech. High school football games were held early or delayed. Some government services closed, and social events were cancelled. If you’re headed out, check road conditions and openings first.

Gov. Nikki Haley declared a state of emergency and directed local and state agencies to coordinate resources. Haley said in an announcement on her Facebook page that parts of the state could experience significant flooding.

“Our family encourages you and your families to stay safe,” she wrote.

Charleston County emergency management was put on alert Thursday afternoon and warned residents of the possibility of an emergency or disaster situation. The county didn’t activate its emergency operations center but said officials were closely monitoring the heavy rain and hurricane threat.

Several of the county’s downtown facilities also were slated to close Friday.

“Our main concern right now is with the heavy rains we are experiencing and have been experiencing since yesterday and will continue to experience throughout the weekend,” said director Cathy Haynes. “We’re working very closely with our municipalities and helping them coordinate. We’ll coordinate with them if they need any resources as a result of any flooding or any types of situation that may occur over the weekend.”

She said the last time the county was put on alert for a potential emergency was during the ice storms in 2014.

In Charleston, the traffic became a problem by Thursday afternoon. The low-lying areas around the Medical University of South Carolina had flooded, and cars were having a difficult time coming onto the peninsula from West Ashley and James Island. Traffic backed up on the bridge over the Ashley River.

The weather service called for 6-10 inches of rain through Sunday for Charleston, Berkeley and Dorchester counties, and more in some spots, with the heaviest rain falling farther north.

Friday’s chance of heavy rain is 100 percent, with 1 to 2 inches possible. Saturday’s chance of heavy rain is 90 percent, with another 2 to 3 inches possible. Sunday had an 80 percent chance with half an inch expected, according to the Thursday forecast.

In an unusually widespread weather event, torrential rains are plaguing the entire East Coast, flooding submerged cars, shutting down roads, and leading to at least one death Thursday, a Spartanburg woman.

An area of low pressure in the Southeast and a front stalled over the East Coast will pull moisture from the Atlantic Ocean, causing rain over the next few days, said Bruce Terry, lead forecaster for the government’s Weather Prediction Center.

Governors up and down the coast warned residents to prepare for the rain and Hurricane Joaquin, which was a Category 4 lashing the Bahamas Thursday night. The East Coast rains could cause power outages and close more roads. The Coast Guard in Charleston warned of dangerous rip currents due to the hurricane.

In Spartanburg, one man was rescued Thursday morning after his vehicle was swept off the road where a culvert had washed out, Doug Bryson with Spartanburg County Emergency Management told local news outlets. The man managed to cling to a tree and was taken to a hospital for treatment, though there was no immediate word on his condition.

Spartanburg County Coroner Rusty Clevenger said 56-year-old Sylvia Arteaga of Spartanburg died Thursday morning. She was driving under an overpass just outside city limits when her car flooded “to capacity” inside.

The Charleston County School District, Berkeley County School District and Dorchester District 2 canceled school Friday, citing the weather. A makeup day for CCSD is scheduled for Oct. 23.

Blaik Doornboss, a College of Charleston student who lives in West Ashley, was going to go downtown to the school’s library Thursday afternoon. He got as far as Savannah Highway and Wesley Drive before deciding to turn around and go home. “Traffic is crazy,” he said. “I’m going to scrap it.”

Doornboss drives a pickup truck, so he wasn’t worried about making through standing water. “I can get through it,” he said, “but the issue is the traffic. He said he’s not sure how the weather will affect his weekend. “But if it’s raining,” he said, “I’m not going downtown.”

Mike Morfopulos had a harrowing ride from his home downtown to West Ashley, where he was waiting for a friend to pick him up for a trip to Greenville. Some other friends drove him in an old truck to the pickup spot. The air conditioning didn’t work, so the windows fogged so badly it was hard to see the road, he said.

At the same time, they were driving down flooded streets through water as high as the doors. “I’m glad to get away from this,” Morfopulos said. “It’s awful.”

Melissa Boughton, Diane Knich and The Associated Press contributed to this report.