Thousands of people have been rescued from their homes and cars as up to 18 inches of rain caused severe flooding in North Carolina.
As the storm made its exit to the sea, the death toll in the US climbed to at least 14, half of them in North Carolina.
"As the sun rises in North Carolina and the blue sky returns, our state is facing major destruction and, sadly, loss of life," governor Pat McCrory said as the effects of Saturday's deluge became clearer.
However, the full scale of the disaster is not yet known as many places have not been reached by rescue teams and four people remain missing in the Fayetteville area of the state.
Weather forecasters said North Carolina and Virginia could get even more rain and warned of the danger of life-threatening flooding through Monday night.
Shortly before daybreak on Sunday the storm was stripped of its hurricane status and downgraded to a post-tropical cyclone.
Matthew - which was a category 5 storm when it hit Haiti last week killing nearly 900 people - made landfall in the States on Friday.
As Hurricane Matthew approaches Florida, its 140-mile-an-hour winds have already left behind a trail of destruction in Haiti.
Residents told to fully prepare for the arrival of the hurricane with warnings its impact could be "devastating".