Tropical Storm Isaac is now a category 1 hurricane heading towards to the Louisiana-Mississippi coastline.
It is expected to reach land on Wednesday close to New Orleans seven years after the city was devastated by Hurricane Katrina.
Evacuations have been ordered in low-lying areas and states of emergency are in effect in Louisiana, Mississippi, Alabama and Florida.
President Obama warned the population not to underestimate the storm:
“We are dealing with a big storm, and there could be significant flooding and other damage across a large area. Now is not the time to tempt fate, now is not the time to dismiss official warnings. You need to take this seriously”
Isaac killed 22 people and caused widespread flooding and destruction in Haiti and the Dominican Republic before touching the southern tip of Florida on Sunday.
Top winds are expected to reach 145 kilometres and hour.