Gordon has “strengthened” in the last few hours, according to the latest update from the National Oceanic and Atmospheric Administration (NOAA).
Gordon was located just 95 miles (155km) south of Biloxi, Mississippi, and 90 miles (145km) south of Mobile, Alabama, NOAA said in its 10pm BST update (4pm CDT).
A hurricane warning is in effect for Mississippi, Louisiana and Alabama as the massive tropical cyclone is expected to exceed hurricane-force wind speeds of 74mph by the time it hits tonight.
What time will the tropical storm make landfall as a hurricane?
The huge storm is headed towards the US Gulf Coast at a rate of 15mph and is expected to hit the Mississippi and Louisiana border late on Tuesday night.
The “earliest reasonable arrival time of tropical-storm-force winds” could be expected at about 2am BST Wednesday (8pm CDT Tuesday night), according to NOAA’s estimations.
Huge wave swells, heavy rain and gale-force winds are likely to smash the Gulf Coast, with as much as 12 inches (30cm) of rain forecast to hit the border area.
A state of emergency has been declared in Louisiana by its governor John Bel Edwards.
Gordon is expected to weaken after moving ashore but government officials are taking no chances with emergency shelters being set up in Mississippi as a precaution.
Residents in South Mississippi have already been warned to prepare for evacuation by The Mississippi Emergency Management Agency.
However, some people have chosen not to budge despite the incoming storm.
Kristin Smith, general manager of The Inn at Ocean Springs and The Roost Hotel in Ocean Springs, Mississippi, said some guests were staying put.
She said: “A lot of guests are real comfortable sticking it out in our rooms.
”Any of our guests who feel like they want to go home we encourage them to follow their instincts.”
The US Coast Guard has warned the ports of New Orleans and Gulfport and Pascagoula, Mississippi, may have to close within 48 hours.
Where will Gordon head after making landfall?
Once Gordon hits land, it will continue on a northwest trajectory through Mississippi into Arkansas before curving right through Missouri.
What are the current storm warnings and watches in place?
A Storm Surge Warning is in effect for Shell Beach to Dauphin Island
A Storm Surge Watch is in effect for West of Shell Beach to the Mouth of the Mississippi River, and East of Dauphin Island to Navarre
A Hurricane Warning is in effect for Mouth of the Pearl River to the Alabama-Florida Border
A Tropical Storm Warning is in effect for West of the Mouth of the Pearl River to the Mouth of the Mississippi River, including Lake Pontchartrain, plus the Alabama-Florida Border to Okaloosa-Walton County Line
All warnings pose a possible threat to life, NOAA has stated.