Animal social networks have been studied intensively in the last decade, but there are relatively few studies of their temporal stability and variation, including the influence of season. We quantified the social network structure across time of a population of wild giraffe, Giraffa camelopardalis, in South Africa. Our aim was to investigate differences between dry and wet seasons and stability across years of giraffe social structure. We found temporal stability in terms of association patterns across years, including between seasons, for the population as a whole and for each sex separately. A comparison of the mean social connectedness of individuals between the wet and dry seasons revealed significant differences, with individuals having more social ties and being stronger socially connected in the wet season. Further analyses revealed that this result stemmed from differences in female–female and intersexual associations, whereas there was no evidence for social connectedness among males being affected by season. In summary, while the extent of social connectedness differed between seasons, the overall social connection pattern of the population was stable over time. This study underlines the importance of long-term surveys of wild animals and their social networks and demonstrates that animals can adapt their social behaviour to ecological changes while simultaneously maintaining a stable social structure.