A door assembly for an agricultural storage bin includes an exterior chute communicating with a lower portion of a bin door opening. The exterior chute extends outwardly at an upward inclination from a bottom edge of the door opening to an open top end spaced below a top end of the door opening. An inner door panel hinged at an inner side of the bin wall spans an upper portion of the door opening above the exterior chute when closed. A cover member spans an open top end of the exterior chute when closed. An unloading auger can be readily inserted through the external chute below the inner door panel for unloading the bin by removing the cover member. The inner door can be subsequently opened inwardly when the level in the bin falls below the upper portion of the bin door opening.