A separator plate in an air-cooled fuel cell comprises a series of airflow channels, each channel extending longitudinally between first and second opposing edges of the separator plate. Each channel has a cross-sectional profile defining an airflow cross-section at points along the length of the channel, and at least selected ones of the channels each have a thermally conductive structure extending into the channel cross-section at selected intermediate longitudinal positions of the channel. The positions are disposed over an active area of the fuel cell, to locally enhance heat transfer from the active area via the plate to airflow moving through the channel.