Abstract: A luminaire that uses Light Emitting Diodes as a light source, and which is intended to be securely mounted outdoors on a pole or arm of widely varying diameter. The luminaire is modular, in the sense that a major component may be removed, repaired and/or replaced for maintenance or for upgrade purposes, without tools, and without modification to any other component in the luminaire. The luminaire's main component is a light engine comprised of Light Emitting Diodes mounted to a thermally conductive circuit board, which in turn is mounted to a thermally dissipative heat sink which resides on the outside of the luminaire. The thermally dissipative heat sink is specifically constructed to take full advantage of horizontal surface winds at the recommended mounting height of the luminaire, to aid in the dissipation of heat created by the Light Emitting Diodes and power components.