At least two people have been killed in storms across the region, officials said. In Texas, a man was killed after his kayak capsized in Dickinson Bayou, police said. In Louisiana, a driver died when his vehicle was swept off the road in floodwaters in Bienville Parish, a spokesman for the state's Office of Homeland Security and Emergency Preparedness said.
Louisiana Gov. John Bel Edwards declared a state of emergency in 16 parishes in the northern part of the state and the National Weather Service issued a flash flood emergency for several parishes
Officials warned that floodwaters could rise above a levy and place thousands of homes in jeopardy.
As of 8 a.m. Wednesday, some areas had received well over 8 inches of rainfall. After more than 14 inches of rain fell in Bossier Parish, officials there said they'd closed at least 100 roads and had issued a mandatory evacuation order for residents of 3,500 homes that could be at risk if floodwaters keep rising.
Up to 10 more inches of rain could fall, and floodwaters could rise above the Guideline Levy, Bossier Sheriff Julian Whittington said
"We'll be out there in full force the rest of the evening and night, as long as it takes," Whittington said. "We encourage everyone to get prepared, and try and evacuate. ... You do need to move out."
The flooding, Whittington said, is a "dangerous situation."
"We've had folks who had to be rescued off rooftops, people rescued from cars, clinging to trees," sheriff's spokesman Bill Davis said.
The Sheriff's Office posted video
showing rushing water, pickups stranded in floodwater and people piling sandbags to protect their homes.
Floodwaters damaged some roads and made others impassable, officials said.
Cathy Little of Shreveport, Louisiana, said she's seen flooding there before, but never like this.
She posted videos of flooding in the area on Instagram. One showed a neighbor's home surrounded by water.
And the rains -- part of a slow-moving storm system crawling across the South -- are expected to continue.
Parts of Arkansas and Texas have endured heavy rainfall.
More than 10 inches of rain have fall in Searcy, Arkansas, since Monday. Longview, Texas, has seen more than 8 inches, according to the National Weather Service.
Forecasters warned people to stay off the roads in areas facing heavy rains.
"Most flood deaths occur in vehicles," the National Weather Service said.
Flooding is the leading weather-related cause of death over the last 30 years, according to CNN meteorologists Jennifer Gray and Monica Garrett
The severe storm risk will remain on Thursday, with cities such as New Orleans and Jackson, Mississippi, possibly feeling the impact.