Heavy downpours will raise the risk for flash flooding along the Gulf Coast and lower Mississippi Valley through midweek.
A slow-moving system will tap into moisture from the Gulf of Mexico and drench the region with soaking rain through Wednesday.
The heaviest storms will focus across Louisiana and eastern and central Texas into Tuesday night.
On Wednesday, downpours are forecast to expand farther north and eastward into portions of Mississippi, Arkansas, Tennessee, Kentucky and Missouri.
The storms will be drenching and slow moving, which could trigger flash flooding in some communities, according to AccuWeather Senior Meteorologist Kristina Pydynowski.
Flooding forced the closure of several roads northeast of San Antonio on Monday night, the Texas Department of Transportation reported.
Never drive through a flooded roadway, as it can put the driver, passengers and would-be rescuers in a life-threatening situation.
"Even if no flash flooding ensues, commuters should prepare for slower travel," Pydynowski explained.
"The downpours will create hazards for motorists by reducing visibility and heightening the risk of vehicles hydroplaning when traveling at highway speeds."
Interstates where motorists should remain alert for rapidly changing conditions include 10, 20, 35, 40 and 55.
Rainfall rates could exceed 1 inch per hour in some locations.
On Monday night, over 2.50 inches of rain fell in under two hours at New Braunfels, Texas, a northeast suburb of San Antonio, according to a National Weather Service trained spotter.
Small streams can quickly overflow their banks and spill onto neighboring roads and lands.
A few of the drenching storms could be locally strong, with gusty winds being the primary threat.
Airline passengers may face delays for a time until any stronger storms have safely passed.
While the rain can put a damper on vacations and outdoor plans, it will help ease the recent dryness across the region.
Beyond midweek, while locally drenching storms are still possible across eastern Texas and the lower Mississippi Valley, the heaviest storms are expected to shift northeastward into the Ohio River Valley.