In the second half of the nineteenth century, most European countries began to finance weather observation networks. As aresult, climatological data practices changed fundamentally. Using the example of Switzerland, this paper examines the political, institutional and methodological dimensions of national data archives. The institutionalization of data collection within the national framework meant, on the one hand, that more observations were systematically made and published. On the other hand, it also meant that the monitoring was connected to state boundaries. However, based on their universalistic conception of science, this did not preclude national institutions from striving for international data standardization. The national framework also shaped the process of transforming weather observations into statistical data. This information formed the basis for national climatographies and thus had anation-building effect. According to the Swiss Meteorological Institute, climate data were practically useful and had great potential for research work. However, the epistemic status of data collection was uncertain, since physical approaches to climatology had gained in importance. The anticipation of scientific and practical potential benefits played acentral role for the continuation of data production. The Swiss case study presented here illustrates that climatology was transformed by the process of nation-building, affecting its institutional structure, spatial references, and epistemology.