HOUSTON (REUTERS) -Tropical storm Nicholas moved slowly through the Gulf Coast on Tuesday (Sept 14), drenching Texas and Louisiana with torrential rain, flooding streets and leaving hundreds of thousands of homes and businesses without power.

The damage from Nicholas comes just two weeks after Hurricane Ida killed more than 80 people across at least eight US states and devastated communities in coastal Louisiana near New Orleans.

Heavy rains lashed Texas and Louisiana on Tuesday (Sept 14) as Hurricane Nicholas weakened into a tropical storm, bringing the threat of widespread floods and power outages as it swept down the US Gulf Coast.

No deaths have been reported from Nicholas, which weakened to a tropical depression on Tuesday evening, since it made landfall as a hurricane along the Texas Gulf Coast early on Tuesday, packing 75 mile-per-hour (121 km-per-hour) winds.

Nicholas was expected to drop 1 to 3 inches (3 to 7 cm) of rain per hour across the region by the end of Tuesday, the National Weather Service said. Isolated areas of the Upper Texas Coast and southern Louisiana could see up to 5 inches.

Nicholas was moving out of the Houston area and east toward Louisiana with maximum sustained winds of 35 mph at about 7pm Central Time (8am Singapore time), the National Hurricane Center said in a bulletin.

The storm, moving at 6 mph, was expected to move into Louisiana, Mississippi and the Florida panhandle by Thursday.

Louisiana Governor John Bel Edwards warned against flash floods triggered by the heavy rain as drainage systems were still clogged with debris from Ida and other storms.

"It's vital that we have as many resources as possible to respond to the forecasted heavy rainfall, potential for flash flooding & river flooding across Central & South Louisiana. I urge everyone to be prepared," he said on Twitter on Tuesday.

By late afternoon more than 94,000 customers in Louisiana and 186,000 in Texas remained without power, according to a Reuters tally.

Classes cancelled

Texas Governor Greg Abbott declared states of emergency in 17 counties and three cities, with boat and helicopter rescue teams being deployed or put on standby.

Patrice Johnson, 70, who lives in Texas City, Texas, about 40 miles southeast of Houston, said she was awake all night worrying about trees falling into her property.

"It was a little scary," she told Reuters outside a local grocery store. "It was pretty windy. I was surprised how windy it was."

Jeff Moore, 55, a homeowner in nearby Bayou Vista, said the water rose to his back deck, but that he never lost power, adding: "That would have been terrible."

Houston Mayor Sylvester Turner said there were no injuries or fatalities reported in the city, where crews were cleaning up debris and restoring power. "It could have been a lot, a lot worse," he said.

In Houston, many residents, especially on the south and southeast sections of the city, awoke to power outages, downed trees and water in their homes on Tuesday after Nicholas passed over the area.

The Houston Independent School District and dozens of schools across Texas and Louisiana canceled classes. Houston resumed limited light rail and bus service on Tuesday.

Hundreds of flights were canceled or delayed at airports in Corpus Christi and Houston.

Galveston Mayor Craig Brown told the Daily News that there was heavy street flooding in low-lying areas early Tuesday morning.

"What caught us a little by surprise was the speed of the winds," Mr Brown said of the 80kmh winds that blew through his city of 50,000. "They were a little heavier with more force than we thought."

Galveston County spokesman Tyler Drummond said officials were assessing the damage, but there was no reports of injuries.

"I suspect what we will find is a lot rooftop damage from sustained winds," he said. "It is all isolated. Some homes that had some tree limbs that fell in the yard or on the home."

In Clear Lake Shores, a community of 1,000 people some 40km north of Galveston, kayakers paddled along streets, surveying the damage to businesses, according to footage from KHOU TV in Houston.

Houston, the fourth most populous US city, was devastated in 2017 when Harvey, a Category 4 hurricane, slammed Texas, dropping up to 100cm of rain in some areas and killing more than 100 people.

President Joe Biden declared an emergency for Louisiana and ordered federal assistance for local responders because of the effects of Nicholas, the White House said on Monday.

Although Hurricane Ida knocked off significant amount of refining capacity in the Gulf Coast earlier this month, Texas refineries remained operating as of early Tuesday.