We studied interannual variability and changes over time in selected climate indices in the reindeer management area (RMA) in northern Finland. We present together the knowledge possessed by reindeer herders with information from meteorological measurements over three decades. The practitioner knowledge was gathered via a survey questionnaire addressing herder observations of long-term changes (approximately during the past 30 years) in climatic conditions and their impacts on herding during the four seasons. A set of temperature-, precipitation- and snow-related indices relevant for herding within the RMA was derived from spatially interpolated daily meteorological data (1981-2010). Climatic changes detected based on the measurement data were mainly consistent with earlier studies, and practitioner knowledge was generally in line with the meteorological data. The herders had experienced the largest number of changes during the winter, and the smallest number of changes during the summer. The herders reported various impacts of changing seasonal weather on reindeer condition and behavior, and on herding practices. Adaptation to the changing conditions requires adoption of various coping strategies by the herders in their everyday work, continuous development of professional techniques and practices, as well as support received from the governance of reindeer management. We conclude that holistic understanding of the impacts of climate change and adaptation to changes in the future requires simultaneous analyses of data from different sources, more research co-defined with local practitioners, and co-planned governance solutions. The approach presented in this work can ease the dialogue between the local practitioners, researchers and policy makers.