MIAMI (AP) - Forecasters say Isaac has strengthened into a Category 1 hurricane with 75 mph winds as it makes its way toward Louisiana.
The U.S. National Hurricane Center said Tuesday that Isaac gained strength as it moved over the warm, open waters of the Gulf of Mexico.
Isaac is expected to make landfall over southeastern Louisiana, possibly the New Orleans area, either late Tuesday or early Wednesday.
Residents are hunkered down behind levees fortified after Katrina struck the city seven years ago this week.
Shelters are open for those who chose to stay or missed the chance to get away before the outer bands of the large storm blow ashore ahead of a forecast landfall in southeast Louisiana tonight or early tomorrow. However, with the exception of some low-lying areas, officials have not ordered mass evacuations.
President Obama has issued an emergency declaration for areas of Mississippi under threat of rain and high winds from Hurricane Isaac.
The declaration frees up federal resources to help state and local agencies in dealing with the storm and its aftermath. It makes federal support available to save lives, protect public health and safety and preserve property in coastal areas.
The declaration, issued Wednesday, affects 29 counties in central south Mississippi.
Those counties are Amite, Clarke, Copiah, Covington, Forrest, George, Greene, Hancock, Harrison, Hinds, Jackson, Jasper, Jefferson Davis, Jones, Lamar, Lauderdale, Lawrence, Lincoln, Madison, Marion, Pearl River, Perry, Pike, Rankin, Stone, Walthall, Wayne, Wilkinson and Yazoo.
The president declared a state of emergency in Louisiana late Monday.