GALVESTON, Texas - Hurricane Rita grew into a monster storm with 170 mph sustained winds as it swirled toward the Gulf Coast, prompting more than 1.3 million residents in Texas and Louisiana to flee in hopes of avoiding a deadly repeat of Katrina.

"It's not worth staying here," said Celia Martinez as she and several relatives finished packing up their homes and pets to head to Houston. "Life is more important than things."

As Gov. Rick Perry urged residents along the state's entire coast to begin evacuating well in advance of Rita's predicted Saturday landfall, New Orleans braced for the possibility that the storm could swamp the misery-stricken city all over again.

Galveston, Corpus Christi and surrounding Nueces County, low-lying parts of Houston, and New Orleans were under mandatory evacuation orders as Category 5 Rita drew energy from balmy gulf waters.

Galveston Mayor Lyda Ann Thomas told NBC's "Today" show today that her city is "fairly well emptied, but we're sending our police forces ... with their loudspeakers reminding people that today is the day to leave."

In Houston, Mayor Bill White said residents in low-lying areas and in mobile homes should leave immediately.

"We're the best prepared city in the country but nothing of this magnitude is welcome," he told ABC's "Good Morning America." "There's not much you can do if you have 150-mph winds."

Forecasters said Rita could be the strongest hurricane on record to ever hit Texas. Only three Category 5 hurricanes, the highest on the scale, are known to have hit the U.S. mainland - most recently, Andrew, which smashed South Florida in 1992.

Hundreds of buses were dispatched Wednesday to evacuate the poor and move out hospital and nursing home patients, and truckloads of water, ice and ready-made meals, and rescue and medical teams were on standby in an effort to show the lessons learned in Katrina.

"We hope and pray that Hurricane Rita will not be a devastating storm, but we got to be ready for the worst," President Bush said in Washington.

At 8 a.m. today, Rita was centered about 490 miles east-southeast of Galveston and was moving west-northwest near 9 mph. Wind speed was 170 mph, down slightly from 175 earlier in the day. Forecasters predicted it would come ashore along the central Texas coast between Galveston and Corpus Christi. Rainfall from the storm could reach 15 inches in spots, the hurricane center said.

Hurricane-force winds extended up to 70 miles from the center of the storm, and even a slight rightward turn could prove devastating to the fractured levees protecting New Orleans.

The U.S. mainland has never been hit by both a Category 4 and a Category 5 in the same season. Katrina at one point became a Category 5 storm, but weakened slightly to a Category 4 just before coming ashore.

In the Galveston-Houston-Corpus Christi area, about 1.3 million people were under orders to get out, in addition to 20,000 or more along with the Louisiana coast. Special attention was given to hospitals and nursing homes, three weeks after scores of sick and elderly patients in the New Orleans area drowned in Katrina's floodwaters or died in the stifling heat while waiting to be rescued.

Galveston was already a virtual ghost town. The city's lone hospital was evacuated along with residents of a six-story retirement home.

The coastal city of 58,000 on an island 8 feet above sea level was nearly wiped off the map in 1900 when an unnamed hurricane killed between 6,000 and 12,000. It remains the nation's worst natural disaster.

City Manager Steve LeBlanc said the storm surge could reach 50 feet. Galveston is protected by a seawall that is only 17 feet tall.

"Not a good picture for us," LeBlanc said.

In Houston, the state's largest city and home to the highest concentration of Katrina refugees, geography makes evacuation particularly tricky. While many hurricane-prone cities are right on the coast, Houston is 60 miles inland, so a coastal suburban area of 2 million people must evacuate through a metropolitan area of 4 million people where the freeways are often clogged under the best of circumstances.

By late Wednesday, the blinking taillights of motorists headed north from Houston could be seen from planes landing at Houston's William P. Hobby Airport on the south side of the city. All routes leading north and west were jammed with vehicles.

A family of three, two children in wheelchairs, and a tired-looking woman in hospital scrubs sat in a darkened and deserted bus stop just off Interstate 610, waiting for a ride.

Galveston's mayor said buses used to take people and their pets off the island were running in short supply Wednesday and warned that stragglers could be left to fend for themselves.

Meanwhile, the death toll from Katrina passed the 1,000 mark Wednesday in five Gulf Coast states. The body count in Louisiana alone was put at nearly 800, most found in the receding floodwaters of New Orleans.

Crude oil prices rose again on fears that Rita would destroy key oil installations in Texas and the gulf. Hundreds of workers were evacuated from offshore oil rigs. Texas, the heart of U.S. crude production, accounts for 25 percent of the nation's total oil output.