Tens of thousands of people were making a last minute dash to safety last night as hurricane-force winds closed in on a long stretch of Texas Gulf Coast, a heavily populated area that includes oil refineries, chemical plants and the city of Houston.
Hurricane Harvey was gathering strength as it headed for shore, gusting at speeds of 125 mph on Friday evening.
By 6pm, storm force winds were battering the coast along with blinding sheets of rain hours before the hurricane itself was due to make landfall either side of midnight.
Residents were braced for a storm sea surge and torrential rainfall which will combine to cause what the National Weather Service is classing as “life threatening flooding”.
Authorities say that could make it the worst hurricane to hit the US in 12 years.
Greg Abbott, governor of Texas, said the size and strength of Harvey put in on a par with Hurricane Katrina, which hit New Orleans in 2005 and left more than 2000 people dead as federal agencies struggled to deal with the aftermath. On Friday, he wrote to President Donald Trump asking for federal aid.
He said it was gearing up to be a “major disaster” and urged people to leave.
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“Even if an evacuation order has not been issued by your local official,” he said at a news conference, "if you are in areas between Corpus Christi and Houston, and maybe even some other areas, especially low lying areas, you need to strongly consider evacuating.”
Harvey’s course sees it make land close to the city of Corpus Christie, before circling inland and moving on to Houston in the days ahead.
Many residents, veterans of previous storms, said they were taking the warnings in their stride.
At a petrol station in Houston’s Meyerland neighbourhood, more than a dozen cars waited for fuel as the first high winds hit.
Brent Borgstedte said it was the fourth place he had tried to find fuel.
“I don't think anybody is really that worried about it. I've lived here my whole life," he said. "I've been through several hurricanes.”
Hurricane Harvey was gathering energy from the warm waters of the Gulf of Mexico as it moved slowly towards shore. Meteorologists upgraded it to a category three storm and said it may reach category four by the time it hits land. The last category four storm to hit America was Hurricane Charley in 2004.
This time, authorities say their damage assessments are exaggerated by the risk of catastrophic flooding, with the Nation Weather Service forecasting as much as 40 inches of rain in some areas as the storm front lingers in the area.
The major economic hub of Houston – which is notoriously flood-prone - is forecast to receive about 25 inches.
At the same time, the storm surge is expected to be between six and 12 feet on some parts of the coast.
Airlines have cancelled flights for the entire weekend in the region and workers are using giant sandbags to reinforce a flood wall to east of Houston. Early on Friday morning, 10 sick newborn babies where flown to the safety of Dallas from a hospital in the danger area.
For his part, Mr Trump arrived at Camp David from where he said he would be monitoring developments.
“We will continue to monitor Hurricane Harvey and the preparedness and response efforts of state, local and federal officials. I encourage people in the path of this dangerous storm to heed the advice and orders of their local and state officials,” he said.
White House officials say he is planning to visit Texas next week.
“Storm turned Hurricane is getting much bigger and more powerful than projected. Federal Government is on site and ready to respond,” he added in a later tweet. “Be safe!”
Dennis Feltgen, spokesman for the National Hurricane Centre, said: “We know that we've got millions of people who are going to feel the impact of this storm. We really pray that people are listening to their emergency managers and get out of harm's way."
Harvey’s intensity coupled with its course along a populated area mean years of rebuilding could lie ahead.
“In terms of economic impact, Harvey will probably be on par with Hurricane Katrina," Brian McNoldy, a senior hurricane researcher at the University of Miami, told the Associated Press. "The Houston area and Corpus Christi are going to be a mess for a long time."