A CURFEW has been imposed in Houston to prevent looting after a catastrophic storm that is now the heaviest tropical downpour in US history.

Weather forecasts yesterday delivered hope after five days of torrential rain submerged the nation’s fourth-largest city, with less than an inch of rain predicted and perhaps even sunshine.

But the dangers remain far from over. At least 18 people are dead and 13,000 have been rescued in the Houston area and surrounding cities and counties in south-east Texas, while others are still trying to escape from inundated homes.

Weakened levees remain in danger of failing and a less ferocious but still potent Storm Harvey is on track to slam into Louisiana.

Authorities expect the human toll to continue to mount, both in deaths and in tens of thousands of people made homeless by the storm.

More than 17,000 people have sought refuge in Texas shelters, and that number seems certain to increase, the American Red Cross said.

Houston’s largest shelter housed 10,000 of the displaced as two additional mega-shelters opened on Tuesday for the overflow.

Louisiana’s governor offered to take in victims from Texas, and televangelist Joel Osteen opened his Houston megachurch, a

16,000-seat former arena, after critics attacked him on social media for not helping families displaced by the storm.

In an apparent response to scattered reports of looting, a curfew was put into effect from midnight to 5am, with police saying violators would be questioned, searched and arrested.

“Once we get this thing inland during the day, it’s the end of the beginning,” said National Hurricane Centre meteorologist Dennis Feltgen. “Texas is going to get a chance to finally dry out as this system pulls out.”

But Feltgen cautioned: “We’re not done with this. There’s still an awful lot of real estate and a lot of people who are going to feel the impacts of the storm.”

Houston has asked the Federal Emergency Management Agency for more supplies, including camp beds and food, for an additional 10,000 people, said mayor Sylvester Turner.

Four days after the storm ravaged the Texas coastline as a Category 4 hurricane, authorities and family members reported at least 18 deaths from Harvey.

They include a former football and athletics coach in suburban Houston and a woman who died after she and her young daughter were swept into a rain-swollen drainage canal.

Authorities acknowledge that fatalities could soar once the floodwaters start to recede from one of America’s largest metropolitan centres.

Two 70-year-old reservoir dams that protect central Houston and a levee in a suburb began overflowing on Tuesday, adding to the rising floodwaters.

Engineers began releasing water from the Addicks and Barker reservoirs on Monday to ease the strain on the dams, but the releases were not enough to relieve the pressure, the Army Corps of Engineers said.

The release of the water means more homes and streets will flood, and some homes will be inundated for up to a month, said Jeff Linder of Harris County Flood Control District.

A warning came from one Texas coastal community that it was becoming increasingly isolated as Storm Harvey-fed rains flooded most major roads leading out of the city and swamped a shelter for those displaced in the Houston area.

Jefferson County sheriff’s deputy Marcus McLellan said he was not sure where the 100 or so evacuees at the Bowers Civic Centre in Port Arthur would be sent.

Most of them were perched on bleacher seats to stay dry, their belongings largely stranded on

the shelter floor below them

under about a foot of water, he said.

“People started coming to the shelter on Monday,” McLellan said.

“And now it’s just all the rainfall that’s coming in, and there’s a canal by there also that’s overflowing.”

After five consecutive days of rain, Harvey set a new continental US record for rainfall for a tropical system.

The rains in Cedar Bayou, near Mont Belvieu, Texas, totalled 51.88in as of Tuesday afternoon, a record for both Texas and the continental US, but it does not quite surpass the 52in from Tropical Cyclone Hiki in Kauai, Hawaii, in 1950, before Hawaii became a state.