Francine weakened to a tropical storm late Wednesday after striking Louisiana as a Category 2 hurricane that blacked out more than 275,000 homes and businesses, sent storm surge rushing into coastal communities and raised flood fears in New Orleans and beyond as drenching rains spread over the northern Gulf Coast.

The storm was forecast to be downgraded to a tropical depression Thursday as it churned northward over Mississippi, the U.S. National Hurricane Center said. Some 10 to 15 centimetres of rain were possible in portions of Mississippi and neighbouring states, forecasters said, warning of the potential threat of scattered flash flooding as far-flung as Jackson, Miss.; Birmingham, Ala.; Memphis, Tenn.; and Atlanta.

Francine slammed the Louisiana coast Wednesday evening with 155 km/h winds in coastal Terrebonne Parish, battering a fragile coastal region that hasn't fully recovered from a series of devastating hurricanes in 2020 and 2021. It then moved at a fast clip of 26 km/h toward New Orleans, pounding the city with torrential rains overnight.

There were no immediate reports of deaths or injuries. TV news broadcasts from coastal communities showed waves from nearby lakes, rivers and Gulf waters thrashing sea walls. Water poured into city streets amid blinding downpours. Oak and cypress trees leaned in the high winds, and some utility poles swayed back and forth. 

'Worse than what I expected'

"It's a little bit worse than what I expected, to be honest with you," said Alvin Cockerham, fire chief of Morgan City, about 50 kilometres from where the storm's centre made landfall. "I pulled all my trucks back to the station. It's too dangerous to be out there in this."

Power outages in Louisiana topped 362,546 a few hours after landfall, spread out widely across southeast Louisiana, according to the tracking site poweroutage.us.

Sheltering at her mother's home just outside Morgan City, Laura Leftwich said blasts of wind had swept away two large birdhouses outside. She had a generator powering an internet connection so she could video chat with friends, holding her computer to a window to show them water overflowing in the street.

If the storm had been any more intense, "I wouldn't have the guts to look outside," said Leftwich, 40. "It's a little scary." 

The National Hurricane Center urged residents to stay sheltered overnight as Francine churned inland. Forecasters say the storm's projected path includes New Orleans, about 80 kilometres northeast of where it made landfall. 

The sixth named storm of the Atlantic hurricane season, Francine was fuelled by exceedingly warm waters in the Gulf of Mexico.

WATCH | Bracing for Hurricane Francine: 

Louisiana residents brace for Hurricane Francine's impact

People in Morgan City, La., shuttered shops and boarded up windows amid evacuations as they prepared for Hurricane Francine to make landfall on Wednesday. Saint Mary Parish Sheriff Gary Driskell said officials have readied high-water vehicles and extra patrols in anticipation of the storm.

Much of Louisiana and Mississippi could get 10 to 20 centimetres of rain, with the possibility of 30 centimetres in some spots, said Brad Reinhart, a senior hurricane specialist at the hurricane centre.

Louisiana Gov. Jeff Landry said the National Guard would fan out to parishes impacted by Francine. They have food, water, nearly 400 high-water vehicles, about 100 boats and 50 helicopters to respond to the storm, including for possible search-and-rescue operations.

Luis Morfin, 26, left his RV camper outside Morgan City's levee to hunker down at a friend's home Wednesday night. Winds lashed the windows as they watching a TV powered by a generator. The power was out, but they were prepared to cook steaks and potatoes on a propane stove.

"We knew what we were expecting," Morfin said. "I don't know how good my camper is, but we'll figure that out tomorrow."

Louisiana Gov. Jeff Landry said the National Guard would fan out to parishes impacted by Francine. They have food, water, nearly 400 high-water vehicles, about 100 boats and 50 helicopters to respond to the storm, including for possible search-and-rescue operations.

Since the mid-19th century, some 57 hurricanes have tracked over or made landfall in Louisiana, according to The Weather Channel. Among them are some of the strongest, costliest and deadliest storms in U.S. history.

WATCH | Officials urge those who didn't evacuate to stay put: 

‘Take this storm seriously,’ officials say as hurricane nears Louisiana

'The time to evacuate has now passed,' a top emergency official in Louisiana said Wednesday as Hurricane Francine neared. People who were still in the path were urged to stay put and be cautious.

Biden declares emergency

U.S. President Joe Biden granted an emergency declaration that will help Louisiana secure federal money and logistical assistance from partners such as the Federal Emergency Management Agency. Both Landry and Mississippi Gov. Tate Reeves also declared states of emergency, authorizing them to quickly free up resources for disaster assistance.

The Mississippi Emergency Management Agency said it distributed more than 100,000 sandbags to the southern part of the state and the Department of Education reported a number of school district closures for Wednesday and Thursday.

More than 78,000 commercial real estate properties worth some $143 billion were in the direct path of the storm, financial researcher Moody's Ratings said. Those buildings have a greater than 50 per cent chance of getting hit by winds of at least 80 km/h, the wind speed at which some damage is likely, according to Moody's.

The storm already had the effect of disrupting energy production and agricultural exports, with nearly 39 per cent of oil and almost half of natural gas production in the U.S. Gulf of Mexico offline on Wednesday, according to the offshore regulator. A total of 171 production platforms and three rigs had been evacuated.