Hurricane Sally threatens deadly flooding in southern US
The National Hurricane Center said the storm in the Gulf of Mexico was packing maximum sustained winds of around 85 miles (140 kilometers) per hour.
At 1200 GMT, Sally was located 105 miles (170 kilometers) southeast of Biloxi, Mississippi, and heading in a northwesterly direction at two mile per hour.
It was expected to make landfall late Tuesday or early Wednesday.
Sally is one of five tropical cyclones currently active in the Atlantic Ocean -- a phenomenon only recorded once before, in September 1971, according to meteorologists.
The others are Hurricane Paulette, tropical storms Teddy and Vicky and tropical depression Rene.
"This one is smaller but it's a little bit more direct, but we have it under control," he said. "We have it under watch very strongly."
"We are fully engaged with State & Local Leaders to assist the great people of Alabama, Louisiana, and Mississippi," he wrote, urging people in the storm's path to "listen to State and Local Leaders."
The governors of Mississippi and Alabama both declared a state of emergency ahead of the approaching storm.
"The storm surge projections continue to be worrisome with anywhere from five to eight feet (1.5 to 2.4 meters) of coastal surge," Reeves said.
"We are continuing to be very concerned about the amount of rainfall," he said, adding that some areas could be drenched in as much as 20 inches (50 cm) of rain.
Governor John Bel Edwards of Louisiana, which is still recovering after Hurricane Laura made landfall in the state as a Category 4 storm, told residents Monday to be prepared.
"Be smart and be safe," he tweeted.
There have been so many tropical storms in the Atlantic this year that the UN's World Meteorological Organization, which names them, is about to run out of names for only the second time in history.
The last time was in 2005, the year hurricane Katrina devastated New Orleans.
The latest Atlantic storm, Hurricane Paulette, pounded the island of Bermuda on Monday with Category 2 winds and heavy rains, according to the NHC.
The center also said Tropical Storm Teddy was expected to become a hurricane on Tuesday.