The evacuation takes effect at noon Sunday and affects about 3,000 residents who live in a flood plain.
Mayor James Baker said Saturday he wants to give residents affected by the order time to make arrangements to stay with family and friends. Transportation will be provided until 6 p.m. Sunday for those who need it.
There's an emergency shelter being set up at William Penn High School.
Baker says the state of emergency declaration doesn't apply to businesses or government, and doesn't affect travel.
The city's emergency operations center will open Sunday morning, when the effects of the storm will first be felt.
The storm has also forced some early school closings in Delaware.
The Red Clay School District, Delaware will be closed on Monday and Tuesday, along with the Concord Christian Academy in Delaware.