The aim of this study was to biometrically analyze the behavioral activity of Ixodes ricinus ticks as influenced by season and trend in numbers, based on material collected during three years in the Ślęża Landscape Park within the Ślęża Massif (Lower Silesia, Poland) using a time series decomposition method. The effects of the abiotic factors of air temperature and humidity on this activity were also determined. A total of 2,745 nymphs and adults of I. ricinus was observed and collected from 2001 through 2003. It was the only collected species from the 17 representatives of the family Ixodidae recorded from Poland. The abundance of the common tick in the Ślęża Landscape Park confirms the risk of tickborne diseases in these nature areas that are under legal protection. The chance of being bitten by ticks increases in the spring and autumn when the behavioral activity of these arthropods reaches their highest levels. Predictions concerning the level of tick behavioral activity should take into account not only seasonality but also the effects of random components, which accounted for about half of the tick activity in our study. The method of time series decomposition employed in our research appears to be useful in making such prognoses. Humidity is particularly significant as it can determine the activity of I. ricinus to a large extent.