Tropical storm Harvey has been the most powerful hurricane to strike the southern US state of Texas in more than 50 years.
Since it first hit land on Friday, the state has been inundated, with flooding submerging entire neighbourhoods and forcing the evacuation of tens of thousands of residents.
And authorities are warning the worst is yet to come, with floodwaters predicted to rise as the storm continues.
US president Donald Trump, who will travel to Texas tomorrow, (wed) says, right now, saving lives is the priority.
"Right now, the single most important thing is the safety and security of those still in harm's way, including the first responders, who have been so terrific and brave. Protecting the lives of our people is my highest priority."
The entire Texas National Guard, made up of 12,000 civilian soldiers, has been activated to help in rescue operations.
In Houston, the country's fourth-largest city, emergency services are using helicopters, boats and special high-water trucks to rescue hundreds of people still believed trapped.
A number of schools have closed, as well as the city's two main airports, and thousands of people are without electricity.
Texas governor Greg Abbott says, second to saving lives, the next aim is to make sure all of those affected can access the necessary services.
"Our second goal is to ensure that our fellow Texans have access to necessities: food, water, supplies and power. During our meeting, we were able to get confirmation that power is in the process of being restored in areas that desperately need it."
The storm is expected to remain over Texas's Gulf Coast for the next few days, with some areas possibly experiencing a year's worth of rain over the span of a week.
The threat of flooding is extending into the neighbouring state of Louisiana, where Hurricane Katrina hit New Orleans in 2005.
And although the threat does not include damage on par with what Texas faces, the emotions there are still raw for survivors like Ray Gratia.
"It really evoked a lot of emotions and heartbreak for the people who are going through that now in Houston. Now, with the storm turning slightly this way, it may bring back even more emotion."
In Houston, rivers have already swelled to record levels, forcing federal engineers to release water to keep it from jumping dams and surging into the surrounding homes.
While that is likely to intensify the flooding in suburban Addicks, Houston mayor Sylvester Turner says, if it is not done, the situation would become far worse.
"And they are releasing water, but it's a gradual release, and what they're indicating (is) that, if they don't do it -- let's say they hold back the water and it builds up -- and then it will be forced ... it will go around Addicks, and the situation would be exponentially worse."
With the storm expected to intensify, 30,000 people are projected to be housed in emergency shelters.
But evacuees say they are already struggling to cope.
"We're already crowded. But all they said is that we're getting 800 more people. And it's like, 'What? Where are they going to put us all?' Buses just keep rolling in. And we need everybody's help."
Wall Street analysts are predicting the recovery efforts will be incredibly expensive.
Almost half of the US oil-refining capacity is in the Gulf region, and shutdowns have been extended across the coast, including the nation's second-largest refinery, Exxon Mobil.
Analysts say the floods' path of destruction could destroy up to $20 billion in uninsured property, making it one of the costliest storms in US history.
