A newly formed hurricane is closing in on the US Gulf Coast, threatening several southern US states including Florida, Mississippi and Alabama.
Hurricane Sally made slow progress over the Gulf Coast early Tuesday, crawling onward at 2mph (3km/h), after growing to a category two storm the day before.
It is expected to intensify before making landfall early on Wednesday.
The hurricane will bring up to 2ft (61cm) of rain and 85mph (135km/h) winds to some areas, officials say.
The National Hurricane Center (NHC) said on Tuesday morning that Sally could bring "historic flooding" and that "extreme life-threatening flash flooding" is likely.
The storm is already drenching parts of the US Gulf Coast as hurricane conditions are expected along the Mississippi and Alabama coastlines and north-western Florida.
This year's hurricane season has been particularly active.
For only the second time in recorded history, there are five tropical storms churning in the Atlantic basin at the same time.
Where is it expected to make landfall?
The NHC on Tuesday said it was still too early to determine where Hurricane Sally's centre will move onshore and urged caution throughout the storm's potential path.
"Dangerous storm surge, rainfall and wind hazards will extend well away from the centre," the agency said.
A hurricane warning remains in effect from the mouth of the Pearl River on the Louisiana-Mississippi border, stretching 200 miles (322 km) eastward to Navarre, in north Florida.
Alabama and Mississippi each declared states of emergency in anticipation of the hurricane, which at 12:00 GMT on Tuesday was located 65 miles east of the mouth of the Mississippi River, plodding along northwest with maximum sustained winds of 85 mph.
"Sally is still expected to be a dangerous hurricane when it moves onshore along the north-central Gulf coast," the NHC said.
"Hurricane Sally is headed straight for Mississippi," Mississippi Governor Tate Reeves wrote on Twitter on Monday evening. "This is the real deal, and it deserves your attention."
Louisiana Governor John Bel Edwards, whose state is still recovering from Hurricane Laura last month, tweeted on Monday to warn residents to "be smart and be safe".
The NHC said the storm had shifted and is likely to pass over the coast of south-eastern Louisiana today before making landfall, but could still cause storm surges that could trigger major floods.
"Additional strengthening is forecast tonight and early Tuesday and Sally is expected to be a dangerous hurricane when it moves onshore," the NHC warned.
In New Orleans, residents who live outside the city's levee protection system have been ordered to evacuate their homes.
As of Monday, almost 80,000 homes in Louisiana were without power as a result of Hurricane Laura, which hit three weeks earlier.
In addition to Sally, there are four other tropical cyclones - Paulette, Rene, Teddy and Vicky - swirling in the Atlantic Ocean basin.
If only one more storm is officially named - Wilfred has already been chosen - meteorologists will begin naming new storms after the Greek alphabet.