Hurricane Sally churned slowly towards the coast of the southern U.S states of Alabama, Louisiana and Mississippi on Monday as it intensified into Category 2 storm.
The National Hurricane Center said the storm in the Gulf of Mexico was packing maximum sustained winds of around 100 miles (160 kilometers) per hour.
At 2100 GMT, it was located 145 miles southeast of Biloxi, Mississippi, and heading in a west-northwesterly direction at six mph.
It was expected to make landfall late Tuesday or early Wednesday.
“Additional strengthening is forecast tonight and early Tuesday and Sally is expected to be a dangerous hurricane when it moves onshore,” the NHC warned, using language that refers to a storm of Category 3 or higher at landfall.
Governor John Bel Edwards of Louisiana, which is still recovering from Hurricane Laura, which made landfall as a Category 4 storm, told residents to be prepared.
“Be smart and be safe,” he tweeted.
The governors of Alabama and Mississippi both declared a state of emergency ahead of the approaching storm.