Watch: Desperate Texans answer call to rescue neighbours in their boats as one-in-500-year-storm sinks southern Texas

It's being described as a storm the likes of which the United States has never seen.

1 NEWS' Rebecca Wright reports from the scene of widespread devastation. Source: Breakfast

Hammered by Hurricane Harvey, southern Texas is now being deluged by dangerous and unprecedented amounts of rain.

Whole swathes of the city are underwater, the highways being used by flat bottom boats to access neighbourhoods that completely cut off.

And with emergency services overrun, it's falling to Texans to rescue each other.

In surreal scenes, we’re seeing families breaking through the roofs of their homes with axes, as the water reaches the attic where they've been told to take refuge.

There they wait to be picked up by the hundreds of ordinary people, who've answered the government's call to come out and help with these high water rescues, in their own boats.

Elsewhere, parents are wading through chest high water, with their children floating beside them, on inflatables, in chilly bins, anything that will float.

And 18 rest home residents, stranded and sitting in chest-high water, were eventually rescued after a picture of their predicament went viral on social media.

Right across the city, thousands of people remain stranded, at the hotel where we’re staying, a truck carrying children, parents and pets has just turned up after being rescued from the water.

At the airport another 500 are stranded, the runway is now a river and not expected to be operational again for days.

The advice is for residents to shelter in their homes, officials today on the defensive about why parts of this city were not evacuated.

Now, it’s too late.

Trying to get millions of people out of their homes, into their cars, and onto the deluged roads would be a deadly mistake.

And this devastating rainfall wreaking havoc in Houston is not going away.

The worst fears of the experts are being realised, with at least another day of extreme rain predicted, and many more wet days forecast beyond that.

And as if the hurricane and the rain weren’t enough, now there are tornado warnings and we’re starting to see massive sinkholes opening up.

So, as night falls here again, many are wondering what this city will look like when the sun comes up.