A killer storm that left up to 13 people dead weakened to a tropical depression on Sunday, but US authorities warned the devastation it caused -- including catastrophic flooding -- is far from over.

The Weather Channel is using a new form of reporting with the help of "immersive mixed-reality technology" to keep its viewers updated on tropical storm Florence.

Hurricane Florence crashed into the Carolinas yesterday, knocking down trees and swamping streets with torrential rains and a powerful storm surge, before slowing to a pace that meant it would plague the area with days of flooding.

“Life-threatening" Hurricane Florence edged closer to the east coast of the United States yesterday, with tropical-force winds and rain already lashing barrier islands just off the North Carolina mainland.

Hurricane Florence is on course to deliver a powerful blow to the east coast of the United States, with forecasters warning of life-threatening rainfall and flooding even as it weakened to a Category 2 storm.

Highways are clogged with people fleeing North and South Carolina as monstrous Category 4 Hurricane Florence rumbles toward the eastern US as the biggest storm there in decades.