Abstract: In this paper the preparation of climatic data for the purpose of a dendroecological study in the Repaš forest (Prekodravlje, Croatia) near Đurđevac is presented. The study was part of the research work done for future hydroelectric power plant 'Novo Virje' on the river Drava. As the necessary climatic indicators were not measured in the Repaš forest, data from the nearest Đurđevac meteorological station for the period 1960-1997 were used (air temperature and precipitation were directly measured, and potential evapotranspiration and solar irradiation were modelled). These data were extrapolated backward to the year 1899 by the method of general linear modelling and using the secular data series of the Zagreb-Grič and Osijek meteorological stations. Additionally, the precipitation data were corrected on the basis of data (1987-1991) from the Gola station, which is the nearest to the Repaš forest. A dendroecological analysis of the correlation between the radial increment of a selected pedunculate oak tree in the Repaš forest and the described climatic variables is presented, using multiple linear regression. The climatic variables significantly influenced the radial increment of the observed tree (correlation coefficient 0.664) in the period 1899-1997.