Streets turned into rivers: the Colorado landscape drastically changed as flooding swept the towns and the Boulder area Thursday, with the rainfall expected to last until the weekend. NBC News reports that hundreds of Coloradans are forced to flee their homes, some taking shelter in a local YMCA, with the storm already claiming three lives.

Continuing storms have caused residents to be stranded or driven from their homes with the 'still-developing disaster' preventing rescuers to launch a full operation amid the torrential downpour. Most Coloradans are struggling to get to higher ground with the circumstances seeming to worsen each minute. Watch videos of the flooding here.

Residents are in utter disbelief over the disaster, with YMCA-Boulder spokesperson Andra Coberly telling NBC News that, "It's insane right now, I've lived in Colorado my whole life, and this is nothing that I've ever, ever seen before."

With the death toll at three, authorities are scrambling to do what they can in order to rescue those caught in the storm. The first casualty was reported near Jamestown, with the victim allegedly crushed in a building collapse. The second casualty occurred on Linden Drive in Boulder, and the third casualty was discovered Thursday near Interstate 25. Witnesses say one person was seen being swept away while inside a vehicle, according to NBC News. The victim is considered to be missing as of this time.

The National Guard arrived Thursday night in Boulder to extend humanitarian assistance. Meanwhile, President Obama approved federal disaster assistance for the devastated State the same day, affirming the request made by Gov. John Hickenlooper.

The flooding is one of the deadliest disasters in Colorado history, leaving residents stunned and unprepared. Boulder County Sheriff Joe Pelle told NBC News that, "This is not your ordinary day, this is not your ordinary disaster; All the preparation in the world ... can't put people up those canyons while those walls of water and debris are coming down."

History reveals that the last disaster of such magnitude occurred in July 1976, when the Big Thompson River swelled its banks and killed 144 people.