<p>The Baltic Sea catchment covers an area of 1.75 million km². Due to its substantial size, the climate varies significantly across the region. The eastern and northern regions experience a subarctic climate, whereas the southwestern and southern regions have a maritime climate. However, studies analysing climate change using isotope hydrology methods (e.g. analysis of local meteoric water lines) are few and far between, and some parts of the catchment are not covered by research at all. To facilitate an understanding of the spatiotemporal patterns between the isotopic composition of meteoric waters and the factors that characterise climatic dependencies, local meteoric water lines were constructed and analysed at different points in the Baltic Sea catchment area. The spatial patterns of isoscapes for the stable isotope signatures of δ²H and δ¹⁸O, as well as their temporal changes, were analysed for the Baltic Sea catchment area. A methodology for estimating similarity in the spatial distribution of scalar characteristics was adapted and applied to the study region. This methodological approach enables us to trace the spatial relationships between processes and phenomena that vary across the territory. Using this method, we compared the spatial distributions of the isotopic composition of meteoric waters, air temperature and precipitation.</p>