Emergency response officials characterized Hurricane Ike as both "potentially catastrophic" and a "worst-case scenario" as the giant storm lashed the Gulf Coast, which left cities flooded, residents stranded, and even gas prices spiking in Texas and across the Southeast today.
"Our nation is facing what is, by any measures, a potentially catastrophic hurricane -- not a time, again, to play chicken with the storm," Department of Homeland Security Secretary Michael Chertoff told reporters today. "This storm is so big that its impact is already being felt all along the Gulf Coast. ... This is only going to continue to intensify in the hours to come."
The storm, which is expected to make landfall in or near Galveston, Texas, by tonight or early Saturday, could leave a storm surge of more than 18 feet in that city and more than 25 feet in northeast Beaumont, Chertoff said.
He also predicted that at least 100,000 people would be affected by flooding, and over 7 million people could be left without power for an undetermined amount of time.
The 72 hours after the storm will be "very challenging," Chertoff said.
Patricia Bolton Legg and her husband Rusty are hunkering down in their Galveston home to ride out the storm.
"We have food and water for two weeks, we have a generator hooked to our freezer and a bucket truck for transportation if we need to get out," said Legg.
Legg is confident she can weather the storm because her 1895 Victorian home has survived every hurricane in Galveston, starting with the great 1900 storm that took the lives of 6,000 people. After that storm, the house, which is built on pier and beams, was raised 17 feet off the ground.
"If I have to go to my attic at the top of the house, I'll be another 30 feet off the ground," said the 50-year-old Galveston City Council member who retired in May.
Legg says her Victorian home is built like a ship. It has double walls of 100-year-old petrified wood that are 10 inches thick and covered in cedar siding. It also survived Hurricanes Carla, Rita and Alicia.
The Leggs returned from their summer home in Newfoundland when they heard Hurricane Ike was on the way.
"Oh, yes, we have one more thing -- plenty of wine," said Legg.
Kevin Kolevar, the Department of Energy's assistant secretary of electricity delivery and energy reliability, warned that there will be constrained oil and gasoline supplies from the Washington, D.C., area down to the South as a result of the storm.
Heavy wind and rain in the Galveston area forced the U.S. Coast Guard to launch helicopter evacuations of nearly 100 local residents on the Bolivar Peninsula. More residents are still waiting to be rescued -- many were waist-deep in water.
"It has already started," Coast Guard Capt. Marcus Woodring said today. "The water is already overtopping Bolivar Peninsula. ... There are people down there and they need help, and we have very limited resources to respond."
The Coast Guard also sent swimmers and aircraft to the cargo ship Antalina, about 140 miles southeast of Galveston; the ship has 22 men on board. That rescue had to be called off, however, because of high winds.
"The likelihood of being rescued by an aircraft is rapidly waning," Rear Adm. Brian Salerno said.
This drama is unfolding despite a blunt warning from the National Weather Service to residents of Galveston in advance of the storm: "Persons not heeding evacuation orders in single-family, one- or two-story homes will face certain death."
With hurricane-force winds that extend out 120 miles from its center, the storm, which is as big as the entire state of Texas, is prompting similar warnings up and down the Texas coast.
The center of Ike, now a Category 2 storm with winds of 105 mph, could reach the coast somewhere near Galveston, late tonight or early Saturday morning. Some strengthening is possible before that happens, forecasters warn. A 20-foot storm surge and 50-foot waves are possible. The flooding could stretch well into Louisiana.
The Dallas Convention Center is no longer taking evacuees, with Friday's registered head count reaching 1,189 people. The remaining 250 beds are being saved for those with special needs.
Evacuee Audine Umbricht told ABC News that she was ready to leave the beachfront Texas home where she was staying, but not without her husband or her prized pooch.
"If I couldn't take my dog, I couldn't leave," Umbricht said. "He's my baby."
Umbricht said that she had planned to evacuate this morning, but when she heard that Interstate 87 was closed, her husband called the Coast Guard.
According to Cmdr. David Woods, who rescued Umbricht and her family, many people were similarly caught off guard, despite repeated warnings. His team has been out with three helicopters conducting rescue missions since 8 a.m. No injuries have been reported.
Woods said those air missions will continue as long as weather permits.
"We'll continue as long as we can continue safely," Woods said. "Then we'll suspend operations until this storm moves through."
ABC affiliate KTRK-TV in Houston reports that part of Galveston's historic Strand district is already underwater, despite the presence of a 17-foot sea wall, and even though tropical storm-force winds have yet to reach the island.
In the city's west end, which is nearly underwater, as well, the ocean is now crashing over the top of man-made sand barriers. Hundreds of high-end homes that dot the beach have water underneath them, KTRK reported.
Hurricane warnings are in effect over a 400-mile stretch of coastline from south of Corpus Christi, Texas, to Morgan City, La.
But on its current track, Ike could come ashore near Galveston and within 50 miles of Houston, the nation's fourth-largest city.
"I am deeply concerned about Hurricane Ike. ... I urge my fellow Texans to listen carefully to what the authorities are saying in Galveston County or parts of Harris County up and down the coast," President Bush said today in Oklahoma. "We'll be monitoring this situation very carefully. The federal government will not only help with -- you know, with the pre-storm strategy, but once this storm passes, we'll be working with state and local authorities to help people recover as quickly as possible."
More then a million Texans have evacuated, but in Houston, officials made a bold decision: They did not issue a mandatory evacuation order for the entire city.
The call was made, in part, due to the city's nightmare evacuation of 2005 as Hurricane Rita bore down on the coast. Traffic jams stretched hundreds of miles, and people were stranded without food or gas for days on the impassable highways. More people died in the gridlock than in the storm itself.
There are ongoing fears that the storm surge could push a wall of water up Houston's ship channel, which would create a nightmare scenario for the city. Out of fear, some waited on line for gas on Friday afternoon to find that many gas stations were sucked dry.
Galveston, which sits on an island southwest of Houston, is different, and the issuing of a mandatory evacuation order was never in doubt. But ABC News found many people were determined to ride out the storm.
Scott Lausen has lived in Galveston his entire life. He's still in the same house he grew up in, and he swears it can handle any storm.
"The house was here when we got here," said Lausen, taking a short break from nailing plywood over his windows. "This is the original roof on this house, and I doubt it's going to go anywhere now."
Lausen and his older brother Russell -- along with a few friends -- plan on making the most out of what promises to be a harrowing and dangerous experience.
"We got lots of water, we'll fill up the bathtub, get plenty of gasoline, make sure the generator is working, and lots of beer. If it gets bad enough, you get on the roof, get your surfboard, case of beer and catch a wave out," he said with a laugh.
Officials are hoping residents like Lausen are the exception.
"The most important message I can send is: Do not take this storm lightly," said Chertoff, during a press briefing Thursday. "Do not look back at Gustav and say, 'Well, that turned out to be not as bad as some people feared, therefore, I'm going to gamble with this storm.' This is not a storm to gamble with. It is large, it is powerful, it carries a lot of water with it, and you're much better served being safe rather than sorry."
But other residents in this Galveston neighborhood about a mile from shore said they would stay put, rather than face the excruciatingly slow trek to safer ground on traffic-clogged highways they faced during Hurricane Rita evacuations in 2005.
In a survey of three counties, the Associated Press found that 90,000 people have chosen not to leave, despite dire warnings from forecasters.
Rudy Gonzales is not one of them. On Thursday afternoon, he was packing valuables into a small U-Haul trailer as the storm was about 400 miles from shore.
"Each one you worry about, and each time you think it's going to be the one that really causes the most damage," he said.
Gonzales says he'll come back, but not until the electricity -- sure to go out in the storm -- is restored.
"When you lose power, and you don't have air conditioning or refrigeration, I mean, it's just miserable," he said.
ABC News' Kirit Radia, Jason Ryan and Jennifer Watts contributed to this report.