BATON ROUGE, Louisiana (CNN) -- New Orleans residents can begin returning to their homes on Thursday, Mayor Ray Nagin said Tuesday night, but he urged them to be aware of the hardships they will face.
"The picture's not as good as we thought it would be," Nagin said almost 36 hours after Hurricane Gustav roared into the state with 110 mph winds.
The loss of electrical power was New Orleans and Louisiana's biggest problem. More than half the state's residents -- 1.4 million households -- were lacking electricity Tuesday, Gov. Bobby Jindal said. Some may not get it back for weeks.
LaFourche parish residents, some of the 2 million who evacuated statewide, were allowed to return home on Tuesday, but their homes may be without power for three to four weeks, according to the Times-Picayune newspaper in New Orleans.
Officials in New Orleans said 13 of the 14 transmission lines that supply the area were not working Tuesday.
President Bush will travel to Louisiana on Wednesday to survey areas damaged by Hurricane Gustav, White House spokesman Scott Stanzel said Tuesday.
Bush will talk to local leaders about recovery operations, Stanzel said.
The president declared 34 of Louisiana's 64 parishes a federal disaster area late Tuesday, making residents there eligible for federal aid.
Louisiana was still feeling the effects of Gustav, now a tropical depression, on Tuesday.
The electricity outage is "obviously a huge challenge as we're trying to get critical services back up," Jindal said.
Hospitals were among services suffering from downed electrical lines.
"It's definitely challenging down here," said Terri McNorton of Baton Rouge General Medical Center. Among the center's 295 patients at its suburban and downtown campuses, only those in intensive care got air-conditioned rooms. Staff and visitors were encouraged to use the stairs rather elevators to save power, she said.
Outside New Orleans, some residents were being allowed to return to their homes as early as Tuesday afternoon.
In Mississippi, 92,000 households remained without power, and 108 shelters were housing more than 14,000 evacuees Tuesday in the aftermath of Hurricane Gustav, the state Emergency Management Agency said. Watch damage and flooding in Mississippi »
The agency said wind gusts in some areas were delaying the process of repairing outages.
It also said portions of roads in coastal counties remained closed.
Jindal noted that the levees and flood walls in southeast Louisiana held up to the storm's wind and rains, to the relief of citizens and officials alike, but that water did overtop New Orleans' Industrial Canal.
"As many of you have seen, we do not have reports of widespread flooding in southeast Louisiana," he said. "We do not have the breaches." Watch a tour of an area that had close call with Gustav »
Homeland Security Secretary Michael Chertoff on Tuesday said evacuations and preparation prevented a repeat of Katrina, which flooded New Orleans and killed more than 1,800 people in 2005.
"The only reason we don't have more tales of people in grave danger and more loss of life is because everybody heeded the governor's instructions, the mayor's instructions, the parish president's instructions to get out of town," Chertoff said at a news conference with Jindal.
Seven deaths along the U.S. Gulf Coast were linked to Gustav, including four hospice patients who died during evacuations before the storm made landfall Monday.
The U.S. Coast Guard has not made any rescues or acted on any calls for distress in the Gulf Coast region due to Gustav, a spokesman said Tuesday.
"Not a single rescue, and we have not had to respond to any spills or leaks" along the petrochemical complexes around New Orleans, Petty Officer Larry Chambers said.
As damage assessment teams began aerial flyovers of Gulf Coast refineries and offshore platforms Tuesday, early reports showed that the industry weathered the storm well.
The hurricane's path steered the storm right through the heart of the region's biggest concentration of oil and gasoline producers. The Gulf is home to 25 percent of U.S. oil production.
"We're still in assessment mode, but so far, things are looking good," said Cathy Landry, a spokeswoman for the American Petroleum Institute. "Also, early reports are saying flooding at refineries hasn't happened, which was one of the big problems during Katrina and Rita."
Gustav was reduced to tropical depression status early Tuesday, with top winds of 35 mph, according to the National Hurricane Center. iReport.com: Did you stay? Share your story
Gustav knocked over trees and power poles across the region. High water closed most of U.S. 90 in Mississippi and Louisiana, and winds sent whitecaps cascading over the levees in New Orleans. Watch how Gustav hit one community hard »
Gustav came ashore near Cocodrie, Louisiana -- about 80 miles southwest of New Orleans -- at midmorning Monday and then moved along the coast to the northwest, avoiding a direct hit on the Crescent City. Houma, Morgan City and other coastal cities took the brunt of the storm. See damage map »