With at least five fatalities confirmed as a result of the storm, emergency workers were going door to door in parts of the the state to urge residents to flee rising floodwaters.
More than two feet of water had already fallen in some places and was not expected to stop soon.
At a press conference in Raleigh, North Carolina governor Roy Cooper told residents that if they were safe they should stay put.
“We know people are anxious to go back. But don’t go back until you get the official all-clear. This system is unloading an epic amount of rainfall.”
Mr Trump’s declaration, announced on Saturday by the Federal Emergency Management Agency (FEMA) in relation to eight counties in the state, means additional federal funding can be used to help people in Beaufort, Brunswick, Carteret, Craven, New Hanover, Onslow, Pamlico, and Pender counties.
“Assistance can include grants for temporary housing and home repairs, low-cost loans to cover uninsured property losses, and other programmes to help individuals and business owners recover from the effects of the disaster,” FEMA said in a statement.
It said it also provided assistance to local governments for clean-up efforts following the storm, including building repairs.