Forecasters are warning of a potentially "unsurvivable" storm surge, after a hurricane strengthened to a Category 4 storm as it approached the coasts of Texas and Louisiana.
The Miami-based National Hurricane Centre said Hurricane Laura was packing winds of 220 kilometres per hour and was expected to make landfall along the Gulf Coast overnight.
As an "extremely dangerous" Category 4 hurricane, the second-highest on the Saffir-Simpson wind scale, Laura could pummel the Louisiana and Texas coast with storm surge, extreme winds and flash flooding, the NHC said.
An "unsurvivable storm surge with large and destructive waves will cause catastrophic damage from Sea Rim State Park, Texas, to Intracoastal City, Louisiana," it said.
Storm surges could penetrate up to 50 kilometres inland along parts of the coasts, and peak surge coupled with high tide could see water as high as six metres above normal levels.
"The power of Hurricane Laura is unprecedented, and Texans must take action now to get out of harm's way and protect themselves," Texas Governor Greg Abbott said.
"The conditions of this storm are unsurvivable, and I urge southeast Texans to take advantage of these final few hours to evacuate."
"Your property can be replaced," Mr Abbott said. "Your life cannot be replaced."
President Donald Trump told residents in the path of the storm to "listen to local officials".
"Hurricane Laura is a very dangerous and rapidly intensifying hurricane," Mr Trump tweeted. "My Administration remains fully engaged with state & local emergency managers."
'Not going to play with the good Lord'
Jimmy Ray was among those heeding evacuation orders in Lake Charles, Louisiana.
"We were going to try to ride it out at the house, but we found out that it was going to be too bad," Mr Ray said.
Another evacuee in Lake Charles, Patricia Como, said her sister, her brother, cousins and other family members had stayed behind but she was "not going to take a chance".
"I'm not going to play with the good Lord," Ms Como said.
Craig Brown, the acting mayor of Galveston, Texas, which suffered the deadliest hurricane in US history in 1900 with thousands of deaths, said the authorities were "monitoring this very closely".
The Shark Shack Beach Bar and Grill is boarded up on the nearly deserted Strand Street in Galveston (AAP) Source: The Galveston County Daily News
"We've had good cooperation from our residents on evacuation," Mr Brown said.
"If they want to stay put, then we allow them to do that," he said. "But we do tell them if they stay, they may not have any emergency services available to them."
Angela Jouett, director of evacuation operations in Lake Charles, said the authorities had new protocols in place because of the Covid-19 pandemic.
"People that come in they get their hands sprayed with sanitiser," Ms Jouett said.
"They’re having their temperature checks, and we're also spacing everybody in six foot distancing."
