Hurricane Laura has made landfall in the US state of Louisiana, causing flash flooding and leaving hundreds of thousands of homes without power.
Forecasters earlier warned that the storm, a category four when it struck the coast with winds of up to 150mph (240km/h), threatened to cause an “unsurvivable” storm surge.
Hurricane Laura is one of the strongest storms to ever hit the US Gulf Coast.
Half a million residents have been told to leave parts of Texas and Louisiana.
Hurricane Laura made landfall shortly after midnight local time (05:00 GMT) near the district of Cameron, in Louisiana. By 04:00, it had been downgraded to a category three storm, with winds of up to 130mph (208km/h), the National Weather Service (NWS) reported.
The storm has since been downgraded further, to category two, and is expected to continue weakening as it moves inland.
The NWS said that the “unsurvivable storm surge… could penetrate up to 40 miles inland from the immediate coastline, and flood waters will not fully recede for several days”.
More than 390,000 homes in Louisiana reportedly lost power in the early hours on Thursday, according to the US tracking site PowerOutage. In Texas, more than 100,000 homes suffered power cuts.
The National Hurricane Center (NHC) earlier warned any residents remaining in or near the path of the “catastrophic” storm to “take action now to protect your life… in a reinforced interior room away from windows”.
“Get under a table or other piece of sturdy furniture,” the NHC said, adding: “Use mattresses, blankets or pillows to cover your head and body.”
Television footage showed heavy rain and strong winds lashing the coastal city of Lake Charles in south-west Louisiana. Buildings have reportedly been damaged and trees ripped from the ground.