Tropical Storm Barry is expected to hit the coast of Louisiana and as a result New Orleans.
But there is a problem, parts of New Orleans is already underwater from flooding along the Mississippi River.
Residents of the coast and in the lower Mississippi Valley could see flooding rain with 500 mm possible in the heaviest rain.
This is the first time New Orleans has seen a tropical storm with water levels this high.
The Mississippi River is now at 16 feet.
Mandatory evacuation orders have been issued for two parishes.
States of emergency have been declared in Orleans, Jefferson, St. Bernard, Plaquemines and St. Charles parishes.