Tropical Storm Cristobal made landfall in Southeast Louisiana Sunday evening.
The National Hurricane Center announced that the center of the storm made landfall at 6 p.m. ET along the coast of southeast Louisiana between the mouth of the Mississippi River and Grand Isle. Maximum sustained winds neared 50 mph.
Throughout Sunday, the storm brought bands of heavy rain and storm surge to the northern Gulf Coast as it made its way toward the U.S. coastline.
Tropical-storm-force winds lashed the Gulf Coast, from southeastern Louisiana eastward along the Alabama/Mississippi coastline. Heavy rain and areas of storm surge will continue to impact the northern Gulf Coast throughout the evening.
Midday Sunday, St. Bernard Parish in Louisiana warned of flooding near the Hopedale Marina, with water reportedly rising 8 inches in an hour.
Storm-surge flooding was also reported in several areas of Mississippi, including along Highway 90 in Biloxi, which was closed to motorists from the Bay St. Louis to the Biloxi Bay bridges.
Cristobal will continue inland overnight, moving up across the lower Mississippi Valley, and is expected to gradually weaken to a Tropical Depression by early Monday morning.
The storm will likely bring rounds of heavy rain and the threat of flash flooding across parts of Mississippi, Louisiana and Arkansas throughout Monday.
ABC News' Greg Bradbury, Dan Peck and Ben Stein contributed to this report.