The National Hurricane Center said Delta had reached hurricane strength Monday night, based on data from hurricane hunters.
Delta is forecast to become a major hurricane as it approaches the Yucatan peninsula and enters the Gulf of Mexico.
The system could make landfall as a category 2 storm anywhere along the Louisiana coast to the Florida panhandle later this week.
"It's unfortunante to have another system threaten Louisiana's coastal parishes, but it is a situation we are prepared to handle," said Gov. John Bel Edwards. "It is common for many people to experience hurricane fatigue during a busy season, but we need everyone to take this threat seriously."