Flooding from days of record-setting rain along the east coast of the US has washed out bridges and homes, with forecasters warning wind gusts topping 35mph could down trees and power lines across the Carolinas and Virginia.

At least five weather-related deaths have been reported since rains began along the eastern seaboard, which has apparently dodged the full fury of Hurricane Joaquin hundreds of miles out in the Atlantic.

President Barack Obama declared a state of emergency in South Carolina and ordered federal aid as flood warnings remained in effect for many parts of the east coast.

The steady downpour arose from a slow-moving low-pressure system over the south east that has linked up to a finger of tropical moisture from Hurricane Joaquin.