Despite the growing awareness of the impact of storm runoff on the environment, the data concerning the composition of storm sewer sediments in seasonal and spatial terms remains limited. The objective of the present study was to assess the seasonal variability of selected physicochemical parameters of sediments and to determine their potential as indicators of the urban environment. Sediment samples were collected during four seasons at five locations (W14, W43, W51, D79, D82). The following parameters were examined in the sediments: pH, electrolytic conductivity (EC), total suspended solids (TSS), turbidity (NTU), chemical oxygen demand (COD), total carbon (TC), inorganic carbon (IC), dissolved organic carbon (DOC) as well as forms of nitrogen and phosphorus. The data were then subjected to statistical processing and principal component analysis (PCA). The results demonstrated a distinct differentiation of the sediment composition, contingent on spatial location and the prevailing season. The highest levels of contamination were found in the sediment from point D82 (e.g. COD: 679.5 mgO2/kg, TSS: 600 mg/kg, NTU: 356), particularly during the spring and autumn months. The sediment collected from point D79 exhibited the lowest and most stable values. PCA analysis demonstrated that TSS, NTU, COD, P-PO43-, EC and DOC are the variables that contribute the most to the PCs and therefore the samples can be differentiated on the 2-dimensional PCA mapping. The stormwater system sediments can serve as an effective tool for monitoring the quality of the urban environment and as a source of information on anthropogenic pressure.