One of the most horrifying photos to emerge from Hurricane Harvey, which continues to deluge the US state of Texas, is a group of nursing home residents trapped to the waist in floodwaters.

A photo of the 15 or so elderly residents, who have since been rescued, was shared widely on social media as locals desperately tried to attract the attention of rescuers.

Timothy McIntosh, whose mother-in-law owns the nursing home, posted the photo that was reposted thousands of times.

“La vita Bella nursing home in Dickinson Texas is almost underwater with nursing home patients,” he wrote on Twitter on Monday.

“Need help asap emergency services please retweet.

“This is absolutely not a fake photo. They need help and we are family.”

Mr McIntosh’s efforts helped save the group. He posted after their rescue: “Thanks to all the true believers that re-tweeted and got the news organisations involved. It pushed La Vita Bella to #1 on the priority list.”

Local emergency coordinators confirmed the rescue to local news outlets.

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Thousands of Australians are also among those hunkering down across Texas as tornadoes, historic amounts of rain and catastrophic flooding from tropical storm Harvey hit the region.

With as much as 1.27m of rain forecast in some areas, Australia’s Department of Foreign Affairs and Trade is urging Australians to follow the advice of local authorities and monitor media reports.

Coast Guard helicopters are rescuing residents from rooftops, more than 215 highways in Texas have been closed and 3000 national guard troops have been activated.

“The roads are basically a system of rivers right now,” Geelong native David Bryant, who is holed up in his three-storey townhouse in a southern suburb of Houston, told AAP on Monday.

Mr Bryant, 41, who works for BHP Billiton in Houston, took in a friend, his seven-months pregnant fiancee and their cats after they had to flee their home in a different suburb when a tornado struck a short distance away and floods threatened.

“We’re planning to just stick tight here,” he said.

“We have plenty of food and water and have not lost power yet.”

With mobile phone coverage and internet still working despite the carnage, Mr Bryant, has been able to keep in touch with his Australian teammates and other expatriates.

Another Australian, Morgan Hughes, a co-owner of Houston’s Platypus Brewing pub, said his home was in the elevated suburb, The Heights, but he was cut off from the brewery.

He could monitor the pub via surveillance cameras and it appeared to have also avoided the flooding.

“A lot of Australians live in The Heights as well and it has become its own island right now so I can’t get to the brewery,” Mr Hughes told AAP.

“I’ve checked in on all of our staff and friends and they have hunkered down and most are fine but some have had some issues.

“I have one Aussie mate who has water in his house.

“It is going to continue be pretty rough.”

Harvey, which hit the Texas coastline on Friday as a category 4 hurricane with 209 km/h winds, has developed into a slow-moving tropical storm that is dumping unprecedented levels of rain on the region.

The disaster has evoked painful memories of Hurricane Katrina, which breached levees in New Orleans in 2005, stranding about 30,000 people in squalid conditions at the Superdome, a football stadium and convention centre.

The evacuees spent days packed inside the sweltering stadium without electricity or running water. The stadium, whose roof peeled off in the howling wind, allowing rain to pour in, became known as a squalid shelter of last resort.

A US insurers group, the Insurance Information Institute, has already warned the flood damage from Hurricane Harvey could equal that of Katrina, which resulted in claims totalling more than US$15 billion.

– with AAP