After Hurricane Ida flooded the Louisiana shore and wreaked havoc on the power grid, rescuers in boats, helicopters, and high-water trucks rescued hundreds of people trapped by the storm's floodwaters.

Residents living in the midst of the state's Gulf Coast's network of rivers and bayous sought refuge in their attics or rooftops, posting their addresses on social media with directions for search-and-rescue teams on where to find them.

Ida, one of the most powerful hurricanes ever to reach the US mainland, knocked out power to more than 1 million homes and businesses in Louisiana and Mississippi, including the whole city of New Orleans.

Officials warned that the damage was so significant that it could take weeks for the electricity grid to be rebuilt.

On Monday afternoon, the storm was downgraded to a tropical depression and continued to make its way inland with torrential rain, causing at least two deaths: a motorist who drowned in New Orleans and a person injured by a falling tree outside Baton Rouge.

However, with many roads inaccessible and cellular coverage down in some areas, the full magnitude of the disaster was still being realized.

“We're going to have many more confirmed fatalities,” Christina Stephens, a spokesperson for Governor John Bel Edwards, stated, based on the level of destruction.

Damage to the electricity grid appeared to be "catastrophic," which is bad news for those without refrigeration or air conditioning during the dog days of summer when highs are expected to reach the mid-80s to around 90 degrees by midweek.

“There are certainly more questions than answers,” Mr. Edwards said at a press briefing. I won't be able to tell you when the power will be restored. I can't say when all of the debris will be cleared up and repairs will be performed.

“But I can assure you that we will work tirelessly every day to provide as much assistance as possible.”

By Monday afternoon, local, state, and federal rescuers had rescued at least 671 individuals, he added.

Rescuers rescued individuals from flooded homes on a near-constant basis in hard-hit LaPlace, which is sandwiched between the Mississippi River and Lake Pontchartrain.

On the 16th anniversary of Katrina, the 2005 storm that burst New Orleans' levees, destroyed the city, and claimed 1,800 lives, the hurricane made landfall.

New Orleans looked to have avoided the devastating flooding that city officials had predicted.

Because of the absence of power and fuel, the city advised people who had evacuated to stay away for at least a few days.

Collin Arnold, the chief of emergency preparedness, stated, "There aren't a lot of reasons to come back."

In addition, the state Health Department reported that 18 water systems servicing around 255,000 people in Louisiana were shut down.

According to the Federal Emergency Management Agency, four Louisiana hospitals were destroyed and 39 medical facilities were forced to rely on generator power. Hundreds of more patients were being evacuated to neighboring cities, according to officials.

Over 2,200 refugees were staying in 41 shelters, according to the governor's office, with the number anticipated to climb as people were rescued or escaped flooded homes.

Slidell, Louisiana, received at least 15.7 inches of rain, while New Orleans received over 14 inches, according to preliminary measures. Other portions of Louisiana and Mississippi, as well as Alabama and Florida, received five to eleven inches of rain.

According to the Louisiana National Guard, 4,900 personnel have been activated, with 195 high-water vehicles, 73 rescue boats, and 34 helicopters on standby.

Hundreds more were being added by local and state agencies. Mr. Edwards said he decided not to fly around the hurricane damage on Monday in order to add another plane to the operation.

According to Entergy and municipal authorities, the hurricane twisted and destroyed a massive tower that carries crucial transmission cables across the Mississippi River to the New Orleans area, creating extensive disruptions.

More than 2,000 miles of transmission lines, as well as 216 substations, were out of operation, according to the power provider. Katrina had not destroyed the tower.

Utility poles were destroyed, trees were thrown onto power lines, and transformers exploded as a result of the storm.

The governor announced that 25,000 utility personnel had arrived in the state to assist in the restoration of power, with more on the way.

“We're going to press Entergy to restore power as soon as they can,” Mr. Edwards said.

AT&T stated its wireless network in Louisiana had been cut to 60% of normal, but that it was recovering. Many people turned to walkie-talkies to communicate.

Ida's winds of 150 miles per hour (230 kilometers per hour) tied it for the fifth-strongest storm to ever impact the mainland. Around midday on Monday, the winds had slowed to 40 mph (64 kph).

Floodwaters engulfed large neighborhoods in Mississippi's southwestern region, and many highways were inaccessible.

According to the National Weather Service, several tornadoes were reported, including one in Saraland, Alabama, that ripped part of the roof off a motel and flipped an 18-wheeler, wounding the driver.

On Monday night, Ida was forecast to gather up speed before dumping rain on the Tennessee and Ohio River valleys on Tuesday, the Appalachian mountain region on Wednesday, and the nation's capital on Thursday.

Before Ida blows out to sea over New England on Friday, forecasters expect catastrophic flooding and mudslides along its route.