Hurricane Ike is already battering communities on the Texas coast as the storm's centre approaches land, with tropical storm-force winds ripping through seaside communities and waves as tall as five metres crashing over seawalls.
Stretching almost 1,000 kilometres wide, the heart of the storm is expected to make landfall in coastal areas as early as midnight ET on Friday.
Forecasters predict it will then move inland directly over Houston, the fourth-largest U.S. city.
According to the U.S. National Weather Service, the storm surge, or wall of water being pushed towards Texas by the hurricane, could cause floods of up to seven metres above sea level — enough to submerge some homes on the low-lying island of Galveston.
Despite an evacuation order issued for Galveston on Thursday, about 90,000 people remained there Friday, according to authorities.
"I believe in 'the man up there,' God," said William Steally, a 75-year-old retiree who opted to remain in Galveston without his wife or sister-in-law. "I believe He will take care of me."
People living in low-lying areas in Galveston could "face certain death" if they ignore orders to evacuate, the National Weather Service has warned. An 8 p.m. curfew will be in effect for residents who choose to stay on the island, Galveston Mayor Lyda Ann Thomas said Friday afternoon.
City officials also announced that, as of 9 p.m., all emergency staff would be called in off the streets, and there would be no more response to calls for help.
Fire crews in Galveston rescued at least 300 people as they waded through flooded streets in search of refuge.
"We were going street by street seeing people who were trying to escape the flood waters," Fire Chief Michael Varela said. "I'm assuming these were people who made the mistake of staying."
Three buildings were destroyed by fire in Galveston because water was too high for fire trucks to navigate.
The city has made some emergency shelter spaces available in a local gym for residents who no longer feel comfortable staying in their homes. People who insist on staying in their homes are being urged to prepare for the worst.
Houston residents told to stay put
U.S. officials, however, are telling Houston's more than two million residents to stay put while Hurricane Ike moves over the city, even as they issued mandatory evacuation orders for about one million people in the surrounding coastal areas.
Houston residents should not flock to the roadways en masse, officials warned, fearing it could create the same kind of gridlock that cost lives when Hurricane Rita threatened Houston in 2005.
Instead, residents have been told to prepare for heavy flooding, power outages and damage to property after the massive storm makes landfall, the weather service said Friday morning.
"It will be, in candour, something that people will be scared of," Houston Mayor Bill White said.
"A number of people in this community have not experienced the magnitude of these winds."
Authorities urged people "just to stay home because there is no way to evacuate that many people," NBC reporter Ken Kalthoff told CBC News.
"It's a pending disaster here, but hopefully there will be no loss of life — that's what they're trying to avoid here," he said from south Houston.
Ike was still a Category 2 storm with maximum sustained winds near 177 km/h Friday afternoon, but was expected to have grown into a Category 3 storm by the time it hit the coast, according to the U.S. National Hurricane Center.
As of 11 p.m. ET, Ike was centred about 88 kilometres southeast of Galveston, moving at 19 km/h.
Hurricane warnings were in effect over a 650-kilometre stretch of coastline from south of Corpus Christi. Tex., to Morgan City, La., and many residents who fled Hurricane Gustav two weeks ago only to be spared in East Texas were packing up again on Thursday.
Oil rigs shut down
Ike's path could see it barrel through some of the 4,000 offshore oil rigs that dot the U.S. Gulf Coast.
Oil prices rose to over $102 US a barrel on Friday after the U.S. Department of Energy shut down production in most of the refineries in the area Thursday.
"Some 95.9 per cent of the Gulf of Mexico's 1.3 million barrels per day of oil production and 73.1 per cent of its 7.4 billion cubic feet per day of natural gas production has been turned off," the department said.
Ike would be the first major hurricane to hit a U.S. metropolitan area since Katrina devastated New Orleans in 2005. For Houston, it would be the first major hurricane since Alicia in August 1983 came ashore on Galveston Island, killing 21 people and causing $2 billion in damage.
Ike is so big, it could inflict a punishing blow even in those areas that do not get a direct hit.
Forecasters warned that because of Ike's size and the shallow Texas coastal waters, it could produce waves up to 15 metres high. It could also dump 250 millimetres or more of rain.
"I cannot overemphasize the danger that is facing us," Texas Gov. Rick Perry said.
"It's going to do some substantial damage. It's going to knock out power. It's going to cause massive flooding."
Rush to run from Rita cost lives in 2005
The decision to tell Houston residents to stay and brace for Ike is a stark contrast to how emergency management officials responded to Hurricane Rita in 2005.
As that storm closed in three years ago, the region drew up a plan to evacuate the two million people in the coastal communities first, past the metropolis of Houston. Once the coastal residents were out of harm's way, Houston would follow in an orderly fashion.
But three days before landfall, Rita bloomed into a Category 5 and tracked toward the city. City and Harris County officials told Houstonians to hit the road, even while the population of Galveston Island was still clogging the freeways.
It was a decision that proved tragic, as 110 people died during the effort, making the evacuation more deadly than the eventual Category 4 storm, which killed nine.