The National Hurricane Center said tropical storm warnings extend from Grand Isle, La., eastward to the Aucilla River in Florida, near the eastern end of the Florida panhandle. The warning zone includes New Orleans and Lake Pontchartrain.
"While Ida appears to be weakening, we urge that residents, particularly in low-lying, flood-prone areas, continue to be vigilant, prudent, and alert to any changes," said Mississippi's governor, Haley Barbour, in a statement from Washington, D.C. where he was traveling.
Florida, Louisiana, Alabama and Mississippi have all declared states of emergency, and though mandatory evacuation orders were canceled, people in low-lying areas or mobile homes were still urged to get out of the storm's way.
"People are already heading out," said Grand Isle resident Neal Perrillioux. "They aren't taking any chances."
"Driving rain" was reported along the Alabama coast this afternoon. Forecasters said residents in the warning area could get 3 to 6 inches of rain, with as much as 8 inches possible in some spots.
Late today Ida was moving to the north-northwest at 18 mph. Its center was about 60 miles from the mouth of the Mississippi River, and about 160 miles from Mobile and Pensacola, Fla., said the hurricane center.
Tropical-storm-force winds -- 40 mph or more -- spread 200 miles from Ida's center.
The storm is projected to make a sharp easterly turn after landfall -- bad news for western Florida and South Georgia. Parts of north Georgia, which had record flooding in September, were told to expect an extra 4 inches of rain.
Craig Fugate, the head of FEMA, the Federal Emergency Management Agency, issued a statement: "This storm is a reminder of the importance of personal preparedness and, whether you live in the Gulf Coast or in another region of the country, I encourage you to visit Ready.gov and make sure your family has a disaster plan."
Oil Prices Rise as Rigs Shut Down
Stretches of southeast Louisiana that do not have levee protection are one concern. Forecasters say those areas could have flooding.
There are economic consequences as well, even with the storm still out on open water. The price of crude oil rose $2 today, to $79.43 a barrel, as traders kept an eye on closed or potentially damaged drilling rigs in the Gulf of Mexico. The number briefly went over $80 a barrel. The weakening dollar has played a role in the rising price of crude, which was $32 per barrel last December.
November Hurricanes Rare
Ida has been an aberration after an unusually quiet Atlantic hurricane season. It was only the third storm of the year to reach hurricane strength. Meteorologists said that's probably because of El Nino, a giant swath of warm water that periodically forms along the equator in the Pacific, rearranging the jet streams that blow over it and keeping storms in the Atlantic from wandering very far north.
The Atlantic hurricane season typically peaks in September, and ends Nov. 30.
Ida still managed to cause extensive damage As it crossed over Central America late last week, it caused at least 124 deaths in El Salvador and destroyed 500 homes in Nicaragua.
The U.S. Coast Guard shut down all non-emergency traffic into and out of ports along the Gulf coast.
But some people rolled their eyes at the storm, according to the Associated Press.
"We're not panicking," said Rick McLendon, the owner of the Bayou Shirt Co. in Bayou La Batre, Ala. "After you go through Katrina, it's got to be a big storm to panic. And this isn't."
ABC News' Suzan Clarke, Rich McHugh, Sabrina Parise and Monica Nista contributed to this report. Additional reporting from The Associated Press.