Tropical Storm Nate gained force as it roared toward Mexico's Yucatan Peninsula Friday (local time) after drenching Central America in rain that was blamed for at least 21 deaths.
Forecasters said it is likely to reach the US Gulf Coast as a hurricane over the weekend.
Mississippi Governor Phil Bryant is declaring a state of emergency in Mississippi's six southernmost counties in advance of it's arrival.
Louisiana officials declared a state of emergency and ordered some people to evacuate coastal areas and barrier islands ahead of its expected landfall early Sunday (local time), and evacuations began at some offshore oil platforms in the Gulf.
The US National Hurricane Center said Nate could cause dangerous flooding by dumping as much as 18 to 25 centimeters of rain as it moved over Honduras, with higher accumulations in a few places.
It had maximum sustained winds of 85 km/h by Friday morning (local time) and was likely to strengthen over the northwestern Caribbean Sea on Friday (local time) before a possible strike on the Cancun region at the tip of Mexico's Yucatan Peninsula at near-hurricane strength. It could hit the US Gulf coast near New Orleans.
The storm was located about 175 miles (280 kilometers) southeast of Cozumel, Mexico and had accelerated its north-northwest movement to 33 km/h.
In Nicaragua, Nate's arrival followed two weeks of near-constant rain that had left the ground saturated and rivers swollen. Authorities placed the whole country on alert and warned of flooding and landslides.
Nicaragua's vice president and spokeswoman, Rosario Murillo, said that at least 11 people had died in that country due to the storm.
Earlier Thursday (local time) she had said 15 people had died before later revising to say some of those were still counted as missing.
Costa Rica's Judicial Investigation Organism blamed seven deaths in that country on the storm and said 15 people were missing. Flooding drove 5,000 residents into emergency shelters.
The National Hurricane Center issued a hurricane warning from Grand Isle, Louisiana to the Alabama-Florida border.
The Bureau of Safety and Environmental Enforcement's New Orleans office said in a news release that as of midday Thursday (local time), six production platforms, out of the 737 manned platforms in the Gulf, had been evacuated. No drilling rigs were evacuated, but one moveable rig was taken out of the storm's path.
The agency estimated less than 15 percent of the current oil production in the Gulf of Mexico has been shut-in, which equates to 254,607 barrels of oil per day.