A heat exchanger includes a plurality of flat, multi-channel heat exchange tubes extending between spaced headers. Each heat exchange tube has its inlet end in fluid flow communication to an inlet header through a transition connector. The transition connector has a body defining a divergent flow path extending from an inlet opening in its inlet end to an outlet opening in its outlet end, and a tubular nipple extending outwardly from the inlet end of the divergent flow path through the wall of the inlet header. The tubular nipple defines a fluid flow path extending between the inlet end of the divergent flow path of the transition connector and the fluid chamber of the inlet header. The inlet header has a lateral dimension less then the lateral dimension of the heat exchange tube.