Tropical Storm Arthur was downgraded from a cyclone to a low pressure area along the upper Texas coast as it made landfall and lost wind intensity on Thursday.
Forecasters still expect the storm to cause life-threatening flooding, property damage and disruptions to commerce and travel.
Its remnants were expected to dump 4 to 8in (10 to 20cm) or more of rain across Louisiana, Mississippi, Alabama, Georgia and the Florida Panhandle through Friday, according to forecasters.
Rain was falling at rates of up to 3in an hour in parts of Louisiana and Mississippi on Thursday, prompting flash flooding, tornado warnings and widespread power outages. The region had already been soaked by heavy rain earlier in the week.
Arthur is the first tropical storm of the season in the Atlantic basin. It is expected to continue weakening as it moves across south-eastern Texas and western Louisiana before crossing the south-east US.
Maximum sustained winds were about 35mph (55km/h). All coastal watches and warnings were discontinued on Wednesday, but flooding is likely through Friday over parts of Texas, Louisiana, Mississippi, Georgia and the Florida Panhandle, the hurricane center said.
In the midwest, more than 130,000 homes and businesses were without power Thursday afternoon in Illinois, Indiana, Michigan, Kentucky, Ohio and West Virginia, according to poweroutage.us.
A tornado was reported on Wednesday evening near Effingham, Illinois, about 90 miles (145km) south-east of Springfield. Several people suffered minor injuries, officials said.
Firefighters responded to damaged homes, collapsed structures, car crashes, downed power lines, gas leaks and blocked roads, the Effingham fire chief, Brant Yochum, said.
Damage from strong winds and a possible tornado were also reported in Florence, Kentucky, near Cincinnati, with news video and photos showing roofs and siding ripped off, as well as downed trees and power lines.
The weather service received numerous reports of wind damage across a wide swath, from Iowa and Missouri to Ohio and West Virginia.
The strong storms were expected to move through the central Appalachians to New England on Thursday, the weather service said.
Some communities in Louisiana and Mississippi were distributing sand bags to residents and cleared debris from drainage systems ahead of the storm.
“The main threat from Arthur is going to be a prolonged, multiday, heavy rainfall event that could produce dangerous to life-threatening flash flooding,” the National Hurricane Center director, Michael Brennan, said.
