In many damselfly species a female-limited colour polymorphism is encountered which is assumed to be the result of sexual conflict. Typically, one morph resembles the male's body colouration (andromorph), while the other is dissimilar (heteromorph). Little is known about the extent of temporal variation in female morph proportions at the water where mating occurs. Knowledge about such variation should help to identify the factors that affect female morph proportion and the scales at which these factors operate. The objective of this study is to assess the occurrence of diurnal and seasonal variation in female morph proportions at the water for the damselfly Enallagma cyathigerum. Diurnal variation was evaluated at six nearby populations, while seasonal variation was examined at one of these populations. Furthermore, we considered temporal variation in female morph proportion in relation to proxies of male harassment (i.e., male density and operational sex ratio). Our findings indicate that female morph proportion varies throughout a day but is uniform on a seasonal scale. Variation in female morph proportions could not be explained by concomitant variation in male density or operational sex ratio. We suggest future study of male mate choice may consider temporal variation in female morph proportions at the water.