Flood watches stretch from South Texas to Georgia as system may become Atlantic season��'s first tropical storm

More than 28 million people from South Texas to Georgia were under flood watches on Tuesday as a low-pressure system bringing heavy rain threatened to become the Atlantic hurricane season's first tropical storm, broadcasters reported.

The Weather Prediction Center issued a level 3 of 4 threat for flash flooding through Thursday in parts of Texas, Louisiana, Mississippi and Alabama after rivers overflowed and roadways were submerged in several areas. "Rivers are overflowing their banks, roadways and vehicles submerged," the report said.

An on-scene resident warned drivers to avoid floodwater: "You got them now. Just be careful getting out." Texas Governor Greg Abbott posted video of a water rescue and urged motorists, "Turn around, don't drown," while issuing a disaster declaration covering more than 100 counties in Texas.

Officials reported at least one fatality: a woman in Bandera County northwest of San Antonio died when her vehicle was swept into a flooded creek. A person at the scene said they had checked social media and "cried multiple times," describing the death as "just so sad."

Heavy rain also damaged facilities: affiliate reports said part of the roof at the Beaumont VA outpatient clinic collapsed and forced a temporary closure, though no injuries were reported. In Shreveport, Louisiana, floodwaters stranded drivers and entered several buildings; a Caddo Parish Sheriff's deputy told CNN the sheriff's office received 52 calls for water rescues in roughly six hours, with no injuries reported.

The National Hurricane Center said the system could become a tropical storm if it pushes offshore into the northwest Gulf of Mexico by Tuesday or Wednesday. Broadcasters concluded with a signoff from reporter Lee Walden.

What happens next: the Weather Prediction Center's threat period continues through Thursday for the areas named, and local emergency officials are enforcing warnings and emergency declarations to help coordinate rescues and sheltering.