Hurricane Nate made U.S. landfall in a sparsely populated area in southeast Louisiana, the National Hurricane Centre said on Saturday, warning of sustained winds of 85 mph.
The storm is expected to move north, making a second landfall on the coast of Mississippi later on Saturday.
Nate killed at least 21 people as it barreled through Central America last week, and has since strengthened to a Category One hurricane.
Louisiana issued an evacuation warning and officials from Mississippi and Alabama declared a state of emergency as Nate moved towards the US coast.
Although not as strong as Hurricanes Irma and Maria, which slammed the Gulf Coast in recent months, Nate is expected to bring storm surges and heavy rains.
Although forecasters said Nate would pass east of New Orleans, Mayor Mitch Landrieu warned residents to find safety as "it's gonna to hit you hard, it's gonna to hit you fast."
Landrieu later lifted a 7pm curfew when it became clear the the city would be spared the worst of the storm.
Many cities along the coast remain on high alert with forecasters warning of three to six inches of rain and as much as 10 inches in some areas.
Several Central American countries felt the full force of Nate as it made its way north.
At least 11 people were killed in Nicaragua due to the storm, with several rivers being left swollen.
Costa Rica blamed seven deaths on Nate, with 5,000 people being forced into emergency shelters.
In Honduras, there were three dead and three missing, while a World Cup qualifier between Costa Rica and and Honduras was cancelled on Friday.
Louisiana experienced mass destruction and more than 1,000 people died when Hurricane Katrina ravaged the state in 2005.
It was one of the five deadliest hurricanes in US history.
The US has already been battered by Hurricane Harvey and Irma this year, with Texas and Florida experiencing widespread damage across August and September.