EN
A calculative procedure for seasonal decomposition of time series for individualization of long-term fluctuation in the course of weather was presented on an example of 10 year results of mean, monthly air temperature and monthly sum of precipitations at meteorological point Mochełek near Bydgoszcz. That method can by used in analysis and presentation of hydrothermal conditions assisting agricultural research, provided that additive model of decomposition is accepted.