Houston, Texas, which is home to several thousand Australians, is being ravaged by historic amounts of rain and catastrophic flooding from Tropical Storm Harvey.

Houston is America's energy capital and the site of US headquarters for Australian companies including BHP Billiton, Santos and Woodside.

"There must be a few thousand Aussies here at least," David Bryant, originally from Geelong, said.

Mr Bryant, who works for BHP Billiton and is president of the Houston Lonestars Australian football club, said the large contingent of Australian expatriates in Texas were keeping in contact via social media. 

"We've shared information around with the community that we know here."

Mr Bryant is holed up in a three-storey townhouse in Houston's south.

He went to the supermarket on Friday to stock up on supplies before the storm hit and he said it was "mayhem".

"The essentials aisles were nearly completely empty," he said.

"I did grab a couple of beers, but I also grabbed some milk eggs, water."

Morgan Hughes, a part owner of Houston's popular Platypus Brewing pub, said on Saturday: "There was some heavy rain overnight, we've had a bit of a break, but I think we are going to get wet again.

"I grew up in north Queensland and my parents just went through [Cyclone] Debbie so I'm used to this."

Australia's Department of Foreign Affairs and Trade is recommending that Australians in southern Texas follow the advice of local authorities and monitor media reports.

Harvey, which hit the Texas coastline on Friday as a category 4 hurricane with 209km/h winds, developed into a slow moving tropical storm and is forecast to dump as much as 127 centimetres of rain in some areas.

"This is likely going to be historical rainfall, if not an all-time record," Texas Governor Greg Abbott told reporters on Sunday.

Streets have been turned into rivers, helicopters are rescuing residents from rooftops, more than 215 highways in Texas have been closed and 3000 National Guard troops have been activated.

AAP