Rescue crews raced to rush people and families to safety Monday night in the Houston area -- as Louisiana braced for flooding of its own from the megastorm known as Harvey.

Louisiana Gov. John Bel Edwards warned people in his state that “the worst is likely to come for us here.”

Meanwhile, floodwaters reached the rooflines of single-story homes in Houston and people could be heard pleading for help from inside. The nation's fourth-largest city remained largely paralyzed by one of the largest downpours in U.S. history. And there was no relief in sight from the storm that spun into Texas as a Category 4 hurricane, then parked itself over the Gulf Coast. Nearly 2 more feet of rain is expected on top of the 30-plus inches in some areas of the state.

Harvey “does remain a tropical storm and it’s going to drop an awful lot of rain” on Louisiana, Edwards said at a news conference Monday. “We do have a long way to go with this particular storm.”

“Harvey's circulation is crawling eastward and the center of the storm is forecast to track through the state of Louisiana later this week,” said Fox News Meteorologist Janice Dean. “The steady flow of winds over the Gulf will put Louisiana in line for a steady stream of heavy rain, including cities like Baton Rouge, Lake Charles and New Orleans.”

Southwestern Louisiana could get 15-20 inches of rain from Harvey. Flash floods warnings went into effect through Thursday as areas along the coast faced tropical storm warnings.

Flooding has already taken over localized streets since Sunday, The Weather Channel reported.

An emergency response official in a coastal Louisiana parish said the threat of flooding from Harvey's torrential rains could be "new ground for us."

Harvey has been blamed for at least five confirmed deaths, including a woman killed Monday in the town of Porter, northeast of Houston, when a large oak tree dislodged by heavy rains toppled onto her trailer home. In addition, a Houston television station reported Monday that six family members were believed to have drowned when their van was swept away by floodwaters. The KHOU report was attributed to three family members the station did not identify. No bodies have been recovered.

The flooding was so widespread that the levels of city waterways have either equaled or surpassed those of Tropical Storm Allison from 2001, and no major highway has been spared some overflow. The city's normally bustling business district was virtually deserted Monday, with emergency vehicles making up most of the traffic. Most businesses were closed.

In Louisiana, Danny Lavergne, director of Cameron Parish's Office of Homeland Security and Emergency Preparedness, said approximately 30 roads in the parish were covered with water but remained passable by Monday morning.

"It's far from being over,” Lavergne said, noting that with more heavy rain in the forecast, it’s still “early in the game.”

Edwards tweeted that he's spoken with President Trump, and "thanked him for the quick response to our emergency declaration request."

Edwards requested the emergency disaster declaration on Sunday as a result of Harvey, which Trump approved. The state of Louisana will request additional areas of southern Louisana be added to this request, as necessary.

The Associated Press contributed to this report.