Cain Burdeau and Kevin McGill

– Associated Press

Isaac became a hurricane Tuesday that could flood the coasts of four states with storm surge and heavy rains on its way to New Orleans, where residents hunkered down behind levees fortified after Katrina struck seven years ago this week.

Shelters opened 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 on Tuesday night or early Wednesday. However, with the exception of some low-lying areas, officials had not ordered mass evacuations.

The U.S. National Hurricane Center in Miami said Isaac became a Category 1 hurricane Tuesday with winds of 75 mph. It could get stronger by the time it’s expected to reach the swampy coast of southeast Louisiana.

President Barack Obama said Gulf Coast residents should listen to local authorities and follow their directions as Isaac approached.

“Now is not the time to tempt fate. Now is not the time to dismiss official warnings. You need to take this seriously,” Obama said.

In Houma, a city southwest of New Orleans, people filled a municipal auditorium-turned-shelter. However, in the bayou country of Terrebonne Parish off Highway 24, storms pose a perennial dilemma for those living a hardscrabble life.

While some of the homes along Bayou Terrebonne and other nearby waterways show signs of affluence, this section of Louisiana 24 is mostly lined with trailer homes or small, often run-down houses. Staying could be dangerous, but many here who could be in harm’s way have nowhere to go and little money to get there, especially given the high price of gasoline.

Forecasters warned that Isaac was a large storm whose effects could reach out 200 miles from its center. Water may be worse than wind because the storm could push walls of water while dumping rain to flood the low-lying coast in Louisiana, Mississippi, Alabama and the Florida Panhandle.

So far, the main damage in the United States was political: Republicans cut one day off their presidential nominating convention in Tampa in case the storm struck there, though in the end it bypassed the bayside city. Isaac is also testing elected officials along the Gulf from governors on down to show they’re prepared for an emergency response.

Isaac’s track is forecast to bring it to New Orleans seven years after Katrina hit as a much stronger storm on Aug. 29, 2005.