Hurricane Rita (search) on Wednesday grew into a Category 5 storm with 165-mph winds as it churned over the Gulf of Mexico and was expected to make landfall on the Texas or Louisiana coast later this week.

As many as 1.3 million other people were ordered to clear out along the Gulf Coast (search) on Wednesday, particularly in New Orleans and Galveston, Texas. To avoid any repeats of the toll Hurricane Katrina (search) took on those who didn't evacuate when that storm hit just over three weeks ago, mandatory evacuations for Galveston will go into effect at 7 p.m. EDT.

Katrina's winds reached 145 mph when it reached land. A storm this big has never hit Galveston, Texas.

"After this killer in New Orleans, Katrina, I just cannot fathom staying," 59-year-old Ldyyan Jean Jocque said before sunrise Wednesday as she waited for an evacuation bus outside the Galveston Community Center. She had packed her Bible, some music and clothes into plastic bags and loaded her dog into a pet carrier.

• Click here to track Hurricane Rita.

A Category 5 hurricane is the highest on the scale, with winds above 155 mph and a storm surge usually greater than 18 feet above normal. It results in total roof failure on many houses and buildings and complete destruction of some other buildings and mobile homes.

Such a storm causes all trees, signs and bushes to be blown down and severe damage to windows and doors. Structures standing less than 15 feet above sea level and within 500 yards of the shoreline will see major damage to the lower floors.

• Click here for more information on hurricane categories.

After getting pounded for its sluggish response to Katrina, the federal government is rushing hundreds of truckloads of water, ice and ready-made meals to the Gulf Coast and put rescue and medical teams on standby. FEMA has aircraft and buses available to evacuate residents of coastal areas.

"Up and down the coastline, people are now preparing for what is anticipated to be another significant storm," said President Bush, who signed an emergency declaration for Florida and spoke with Texas officials about the storm's landfall.

Acting Federal Emergency Management Agency Director R. David Paulison (search) said during a press conference Wednesday afternoon that the federal Department of Transportation is mobilizing buses and ambulances to evacuate people. The Defense Department is also mobilizing any useful forces it has to be on ready on a moment's notice.

Paulison also recommended evacuees bring with them at least three days' worth of clothes, medicine, batteries, communication devices and other necessities. He also reminded people to check the federal government's Web site,, for other preparation tips.

"I strongly, strongly urge the Gulf Coast residents to pay very close attention to this storm," Paulison said.

"We are not making any assumptions on this storm ... we're going to make sure this time, make sure we have all the resources to offer. Whatever the government has available, they're going to make sure it's on the ground to help Texas."

Paulison said now is not the time to postulate on what went wrong in dealing with Katrina at both the local and federal level, but added: "I'd rather pre-deploy more assets than we need than not enough."

Homeland Security Secretary Michael Chertoff (search) told residents to heed the calls to leave.

"We've been in very close contact with the governor, with the state emergency managers, talking about their evacuation plans. They've got buses and other vehicles available for people who can't drive themselves out," Chertoff told FOX News Wednesday morning. "They're moving very early on the issue of evacuation and I'm hopeful people will take it very seriously this time."

At 11 a.m. EDT, Rita was centered about 260 miles west of Key West, Fla., and 775 miles southeast of Corpus Christi, Texas, moving west at near 13 mph. Forecasters predicted it would come ashore Saturday somewhere between northern Mexico and western Louisiana, most likely in Texas.

Meteorologist Chris Landsea of the National Hurricane Center in Miami said Rita could strengthen into a terrifying Category 5 with wind over 155 mph as it moves over the warm waters of the gulf, or it could ease to a Category 3, with wind of less than 130 mph.

On Tuesday, Rita skirted past the Florida Keys (search) as a Category 2 storm, causing minimal damage.

Visitors ordered out of the Keys will be invited back Friday, and virtually all other voluntary evacuation orders in South Florida were lifted after Rita roared past.

But the worst is yet to come in other areas.

Texas Gov. Rick Perry (search) said Wednesday that Rita would "quite likely be a devastating storm."

But, he added, "there is no need to panic. We've been preparing for this type of an event for a number of years."

Perry said officials were working to help those who could not evacuate by themselves and strongly encouraged people to "being proceeding to more safe areas."

Perry urged coastal residents from Beaumont-Port Arthur to Corpus Christi to move inland and suggested that residents calmly gather important documents, secure their homes, fuel their vehicles and move away from the shoreline.

A full evacuation of the coast would take at least 33 hours, and Perry warned coastal residents not to wait for a mandatory evacuation order, saying, "homes and businesses can be rebuilt. Lives cannot."

'You're Here at Your Own Risk'

Galveston Mayor Lyda Ann Thomas (search) said the Texas Department of Public Safety and National Guard were available to help following a storm.

"We are very sensitive to the storms here," she told FOX News. "Our communication with the state emergency management people is excellent."

She said during a press conference Wednesday that the inbound causeway into Galveston would be closed starting at 7 p.m. EDT. Thomas said pets should be transported in carriers displaying the animal's name and wear identifying collars.

"We're going to help you get out of the city," Thomas said. "If you choose not to leave, you're here at your own risk."

People can make bus reservations out of Galveston by calling 409-797-3710. Individuals with special needs would be boarded first, followed by those with reservations.

"We're looking for early Saturday morning" landfall, Mary Jo Naschke, the city's public information officer, told FOX News.

"Destination unknown," said Catherine Womack, 71, who was boarding up the windows on her one-story brick house in Galveston. "I've never left before. I think because of Katrina, there is a lot of anxiety and concern. It's better to be safe than sorry."

Houston Mayor Bill White (search) on Wednesday advised all city residents in the storm-surge area to begin making evacuation plans.

For those living in low-lying areas, including east and southeast Houston and locations that have experienced flooding in the past, the mayor added: "Make your plans for voluntary evacuations now."

"We've been advised by emergency management professional that few mobile homes, if any, could withstand" the wind strength of Hurricane Rita, he explained, and urged businesses to give nonessential employees Thursday and Friday off. "We will be making plans and announcements throughout the week."

Mandatory evacuations were to begin in the city of Houston and Harris County on Thursday.

"We need citizens who may need assistance in evacuating to reach out" to family, friends and neighbors, as "there will not be enough government vehicles to evacuate everyone" in the affected areas, White said.

Those who do not have assistance or who need to report an emergency to call 311, or 713-837-0311 for those in areas not accessible to 311. White urged acquaintances of those in need to "open up the generosity of your heart."

Along the Texas Gulf Coast, authorities rushed to get the old and infirm out of harm's way, three weeks after scores of sick and elderly nursing home patients in the New Orleans area drowned in Katrina's floodwaters or died in the stifling heat while waiting to be rescued.

In Galveston, the Edgewater Retirement Community, a six-story building situated near the city's seawall, began evacuating its more than 200 nursing home patients and independent retirees by chartered bus and ambulance.

"They either go with a family member or they go with us, but this building is not safe sitting on the seawall with a major hurricane coming," said David Hastings, executive director. "I have had several say, 'I don't want to go' and I said, 'I'm sorry, you're going.'"

Crude oil prices rose again on concern that Rita would smash into key oil facilities in Texas and the Gulf of Mexico. Hundreds of workers were evacuated from offshore oil rigs, less than a month after Katrina damaged some installations. Texas, the heart of U.S. crude production, accounts for 25 percent of the nation's total oil output.

Race to Fix New Orleans' Levees

In New Orleans, fewer than 1,000 people remained in the city, said Task Force New Orleans' commander, Brig. Gen. Myles Deerfield.

"We're here to preserve lives. ... We're treating it very seriously," he said.

The Army Corps of Engineers raced to patch the city's fractured levee system for fear the additional rain could swamp the walls and flood the city all over again. The Corps said New Orleans' levees can only handle up to 6 inches of rain and a storm surge of 10 to 12 feet.

"The protection is very tenuous at best," said Dave Wurtzel, a Corps official handling some of the repairs.

Engineers and contractors drove a massive metal barrier across the 17th Street Canal bed to prevent a storm surge from Lake Pontchartrain (search) from swamping New Orleans again, and worked around the clock to repair the damaged pumps, concrete floodwalls, earthen berms and waterways that protect the below-sea-level city.

In addition, the corps had 800 giant sandbags weighing 6,000 to 15,000 pounds on hand, and ordered 2,500 more to shore up low spots and plug any new breaches.

The federal government's top official in the city, Coast Guard Vice Adm. Thad Allen (search), said the preparations in and around New Orleans included 500 buses for evacuation, and enough water and military meals for 500,000 people.

Many New Orleans residents were forced once again to decide whether to stay or go.

"We are praying that the hurricane dissipates or that it weakens," said Louisiana Gov. Kathleen Blanco, who declared a state of emergency. "This state can barely stand what happened to it."

Rita created relatively few problems along the Florida Keys, with its eye missing land. Thousands of residents who evacuated were expected to begin returning in earnest on Wednesday.

As of 9 a.m. Wednesday, there were reports of localized flooding. About 8,000 people in Key West had no power as returning residents began taking boards off their homes and businesses.

"We're fairly accustomed to this," said Sen. Bill Nelson (search), D-Fla. "We're mopping up, but the big one didn't hit directly. It's nothing like getting hit with a Category 4."

Nelson figured that Rita would probably lead to another rise in energy costs and gas prices.

Citing concern for senior citizens and low-income residents, he added: "They can't afford to drive to the doctor."

Rita is the 17th named storm of the Atlantic hurricane season, making this the fourth-busiest season since record-keeping started in 1851. The record is 21 tropical storms in 1933. Six hurricanes have hit Florida in the last 13 months.

The hurricane season ends Nov. 30.

The Associated Press contributed to this report.