Updated at 4:32 p.m. ET
Barry reached Louisiana's central coast, near Intracoastal City, on Saturday morning as a Category 1 hurricane, the National Hurricane Center said, before weakening to a tropical storm.
The storm has already brought flooding to New Orleans, where tornado warnings have been issued.
Residents across other parts of Louisiana have also been bracing for flooding — forecasters predict up to 25 inches of rain across much of southern Louisiana and southwest Mississippi, leading to dangerous, life threatening flooding.
"Today is really going to be the day of the biggest impacts from Barry," John Cangialosi, a senior hurricane specialist at the National Hurricane Center, told NPR. Cangialosi said the biggest impacts from the storm will be caused by heavy rains and storm surge.
The hurricane center said a storm surge warning is in effect for much of southeast Louisiana, stretching from Intracoastal City to Biloxi, Miss.
The storm is bringing 75-mph sustained winds, and forecasters say tropical-storm-force winds will extend up to 175 miles outward from the storm's center. Wind gusts topped 65 mph in Dulac, Louisiana, on the southeastern coast.
Parts of Louisiana have already been hit by strong wind and rains that have washed out some coastal roads.
Meteorologists have warned of downed trees and power lines. The Weather Channel's Rick Knabb says the storm's winds will "be strong enough to take down some trees - easier on already saturated soils - that could be life-threatening by falling on cars, roads...or homes."
Across Louisiana, nearly 100,000 people have already lost power, reports the website Poweroutage.us.
Rain bands were moving onshore by the early morning hours, forcing the cancellations of flights to and from New Orleans.
Authorities ordered emergency evacuations in much of Plaquemines Parish and parts of Jefferson Parish southeast of New Orleans.
On Thursday night President Trump declared a federal emergency for Louisiana, allowing the Department of Homeland Security and Federal Emergency Management Agency to begin coordinating relief efforts.
Officials in New Orleans are keeping a close watch on the city's levees, which failed during Hurricane Katrina in 2005, inundating the city with water and leaving an estimated 1,800 people dead.
In New Orleans Lower 9th Ward, resident Burnell Lucien spoke with NPR's Debbie Elliott. Lucien said he believes the city's infrastructure will be able to withstand this hurricane. "The levees are higher," Lucien said. "We don't get the storm surge in the canals no more. If it's just rain water, we good. We good."
Ricky Boyett, a spokesman for the Army Corps of Engineers, told NPR on Saturday, "When you're looking at the federal levee system ... we're in good shape. There are no threats that we're seeing."
Boyett did say, however, that a stretch of non-federal levees are being over-topped. "The big concern is the potential for the over-topping of Highway 23. That's our big focus," he said. Most of that area, in Plaquemines Parish, has been evacuated, according to Boyett.