Fuel shortages and monster traffic jams were reported amid an enormous human exodus from the coast of Texas and south-western Louisiana. On some interstate highways, cars stopped moving entirely. About 1.3 million people from both states were under orders to leave.
While meteorologists acknowledged that some weakening could occur in the storm as it nears the coastline, it still looks certain to make landfall as a highly dangerous category 3, at least. Not only does it promise to bring new human misery to the southern US, it could inflict deep economic wounds. Last night, the storm seemed certain to take a swipe at the heart of America's oil-producing heartland.
What is certain - even before Rita's power is felt on the Texas beaches - is that the storm will be a crucial political test for President George Bush, and the beefed-up national emergency preparations put in place after the botched response to Katrina.
In contrast with his reaction to the impending Hurricane Katrina last month, President Bush will visit Texas today. "He will stop to get a first-hand look at the preparations under way for Hurricane Rita and to show our support for the first responders as they get ready for the response to Hurricane Rita," the White House spokesman Scott McClellan said.
Late on Wednesday, more than 48 hours before Rita was due to slam into the eastern Texas coast, the Bush administration declared the storm "an incident of national significance" - something it failed to do until two days after Katrina - and readied regular army units to help with the relief and rescue operations.
Amphibious vessels carrying 1,000 marines and equipment have taken up position in the region, ready to move in the moment the storm has passed. More than 5,000 Texas National Guardsmen are on emergency stand by.
By nightfall, the path of the storm shifted slightly to the east and north, taking aim at a 100-mile stretch of coast between the city of Galveston and Houston 60 miles inland and the Texas border with Louisiana. Interstate highways heading north were said to be jammed for up to 100 miles.
Typically, a hurricane's worst winds and surges occur on the eastern, right-hand side of the eye, meaning that western Louisiana could bear the brunt of Rita. Governor Kathleen Blanco warned that "massive damage" was possible in that area. But a further shift in the storm's course could bring back into the equation the low-lying city of New Orleans, where engineers are scrambling to repair levees damaged by Katrina.
By late yesterday the outer bands of Rita - a storm measuring almost 350 miles across - were already bringing rain to New Orleans. Indeed, the weather last night was the first significant rainfall in the "Big Easy" since Katrina three weeks ago.
Weathermen warned that every 20 miles of eastward movement by the storm would mean an additional inch of rain in New Orleans. Even a small storm surge could reopen breaches in the levees, allowing more water to pour into a city 30 per cent of which is still flooded.
At noon yesterday, Rita was still a frighteningly powerful category 5 storm, 400 miles south-east of Houston and packing maximum sustained winds of 165mph.
Experts say it will weaken as it approaches the shoreline, but it is still likely to make land as a category 3 or 4 hurricane, which will make it one of the most powerful storms to strike Texas since the hurricane that destroyed Galveston in 1900, the deadliest natural disaster in modern US history.
Last night, state and federal officials were pleading with residents to disregard suggestions that Rita may weaken. "Don't follow the example of Katrina and wait. No one will come and get you during the storm," Harris County Judge Robert Eckels said in Houston.
Getting out of Houston and other urban areas was far from easy, however. Apart from bumper-to-bumper traffic jams, drivers were discovering garages already out of petrol while many grocery shops along the main evacuation routes had been stripped bare of provisions. And as families fled inland, they found in town after town, hotels were already booked solid and shelter was nearly impossible to find.
Though oil rigs, refineries and petrochemical facilities were being evacuated, secured and closed down, some damage appeared inevitable, raising the spectre of industrial pollution.
The political stakes are also huge - for George Bush in particular, whose approval ratings took another battering as the federal government was blamed for its tardy and initially inept response to Katrina.
Since then Michael Brown, the director of the Federal Emergency Management Agency (Fema), was forced to resign, and emergency supplies and satellite communications networks have been pre-positioned throughout the threatened area.
But many senior Republicans are still critical of Mr Bush's subsequent handling of the crisis, in particular his failure to say how the $150bn-plus of government relief and reconstruction spending on Katrina will be covered, at a time when the budget has a near-record deficit.
John Snow, the Treasury Secretary, said this week plans for further tax cuts are being shelved. But Mr Bush is resisting demands for a one-off tax increase to meet the hurricane's costs.Reuse content