Texas Governor Greg Abbott says damage from Hurricane Harvey would exceed that of epic hurricanes Katrina or Sandy, likely reaching US$150 billion to US$180b (NZ$209b to NZ$251b).
Harvey, which came ashore on August 25 as the most powerful hurricane to hit Texas in 50 years, has killed an estimated 47 people and displaced more than 1 million after causing wreckage in an area stretching for more than 480km.
Mr Abbott, who is advocating for US government aid to repair his state, said the damage would exceed that of Katrina, the storm that devastated New Orleans and surrounding areas in 2005, and Sandy, which overwhelmed New York city and the US Northeast in 2012.
"Katrina caused if I recall more than US$120b (NZ$167b) but when you look at the number of homes and business affected by this I think this will cost well over US$120b, probably $US150b to $US180b," Mr Abbott told Fox News, adding, "this is far larger than Hurricane Sandy".
The administration of US President Donald Trump has asked Congress for an initial US$7.85b (NZ$10.97b) for recovery efforts, which Mr Abbott called a "down payment".
Houston was still struggling to recover on Sunday, when the city forced the evacuation of thousands of people on the western side of town who were affected by the release of floodwater that had built up in a reservoir.
The US Environmental Protection Agency on Saturday raised concerns about 13 Superfund sites, heavily contaminated former industrial zones, which had been flooded and were in danger of spreading toxins.
Damage from the storm is also posing an economic and humanitarian challenge for Mr Trump, who visited Houston on Saturday and met some survivors and rescue workers.
The visit gave Mr Trump an opportunity to show an empathetic side, after some criticised him for staying clear of the disaster zone during a Texas visit on Tuesday. Mr Trump said he did not want to hamper rescue efforts.