Water temperature was monitored from May to October 2016 in the Świder and Utrata rivers, two lowland tributaries of the Vistula River in central Poland. Seven temperature recorders were located along each river continuum to examine both anthropogenic and natural factors affecting spatial temperature variability. The results showed that water temperature patterns in quasi-natural sites were generally similar across the length of the rivers. The most pronounced temperature increases were found to be the result of reservoir releases, wastewater inflows, and channel regulations. Riparian shade changes have also been identified as the main driver of spatial temperature heterogeneity, while the impact of the tributaries was not clear and depended on the degree of their anthropogenic transformation. Linear regression performance was similar in the case of most quasi-natural sites in the Świder River, while in the case of the Utrata River differences were found in explanatory power, slopes, and intercepts. Such investigations of water temperature patterns indicate that in lowland rivers temperature variations can be spatially complex and significant in their magnitudes, thus current research could help in the context of riverine management – especially for fisheries and environmental protection.