Forecasters say Hurricane Gustav has strengthened to a Category 4 storm and has maximum sustained winds of near 145 mph (233 kph).
The National Hurricane Center on Saturday called Gustav an "extremely dangerous" storm. The increase in the storm's intensity comes as people line up for buses to take them out of New Orleans. Traffic is also heavier on main highways out of the city as residents head north.
New Orleans has yet to call for a mandatory evacuation, but began ushering out the sick, elderly and those without their own transportation, AP reported.