Seasonal and multi-annual variability of river water temperature has been analysed based on data from 24 gauge stations of the IMGW network. It has been characterised by means of several values of the thermal regime parameters: mean annual, semi-annual (November-April, May-October) and amplitude. The variability of water temperature in the catchment and in the stream network has been estimated. Measurement data included seven stations at the Vistula river. On the background of natural variability, rivers or their segments have been distinguished where water temperature is impacted by anthropopressure.