(CNN) -- As Tropical Storm Cindy is heading toward the Gulf Coast states, millions of people are bracing for heavy rain and potential flash flooding.
At least 17 million people are under a tropical storm warning from San Luis Pass, Texas, to the Alabama-Florida border, said CNN meteorologist Michael Guy.
Between Wednesday and Thursday morning, the storm could bring up to 12 inches of rain to some areas between Texas and Louisiana.
Cindy is just the second tropical storm to form in the Atlantic since the hurricane season officially began on June 1. The center of the storm is projected to make landfall sometime Thursday morning.
Heavy rain and some flash flooding have been reported along the Gulf Coast and southeastern region since Tuesday but more is on the way.
From East Texas to southern Mississippi, Cindy is expected to drop 3-6 inches of rain and some isolated areas could see up to 12 inches of rain, the National Weather Service said.
The storm will make landfall along the coast between Texas and Louisiana by Thursday morning.
The most torrential rain would likely be to the east of the center of the storm, because these areas will see a prolonged period of onshore flow, Guy said.
As the storm comes ashore, the coast could also face strong winds of up to 50 mph.
A 'slow-moving disaster'
For state officials in Alabama, Louisiana, Mississippi and Texas their greatest concern is flooding.
Ahead of the storm, Alabama's Gov. Key Ivey declared a state of emergency to "guarantee state resources are on standby and are ready to assist impacted communities if necessary."
"There's been a lot of rain in the area over the last 3-4 weeks so the ground is pretty saturated," said Glen Brannan, the plans and operations officer with Alabama's Mobile County emergency management agency.
In Mississippi, the city of Biloxi declared a state of emergency saying it's one of the areas in the state with the greatest risk of flooding. Residents in nearby counties were also offered sandbags.
"It's kind of like a slow-motion disaster for us now. It's not wind, it's rain we're concerned about," said Greg Flynn with the Mississippi Emergency Management Service.
Authorities in Louisiana announced they will close courts and other government buildings across the state on Wednesday.
Some summer school programs were also canceled Wednesday in New Orleans and Donaldsonville.
In Texas, elderly residents and families with medical issues living in Bolivar Peninsula near Galveston were encouraged to evacuate their homes.
"The voluntary evacuation order is intended to alert residents of Bolivar Peninsula that emergency responders may be unable to reach them," Galveston County Judge Mark Henry said in a statement.
Texas Gov. Greg Abbott said several emergency operations teams have been activated or are on standby to prepare for the storm's landfall.
"We stand ready to assist local communities in the event of an emergency, and I ask all Texans to keep those in the storm's path, and our brave first responders, in their prayers as they prepare for this storm," Abbott said in a statement.