Türkiye is one of the countries highly vulnerable to climate change. In this study, we focused on the northwesternmost part of Türkiye, between Edirne-Kalkansogut. We analyzed the long-term climatic data series (70 years) from Edirne Meteorological Station and long-term streamflow gauge data from Tundzha (58 years), Sinanköy (27 years) and Çömlek (30 years) rivers. We performed trend analysis and Thornthwaite water budget analysis to understand the temporal patterns of streamflow and climate. Our findings suggest that annual and seasonal average temperatures, evapotranspiration, water surplus, and total precipitation values decreased between 1952–1986 and increased between 1987–2021. Regression analysis results demonstrated an increase in streamflow values between 1986–2018. Furthermore, statistical analysis has highlighted a weak relationship between temperature/evapotranspiration and streamflow, while a strong relationship was observed between streamflow and precipitation. These climate and surface runoff changes hold the potential to significantly impact natural resources in northwesternmost Türkiye, leading to more frequent extreme precipitation events and more damaging natural hazards. Effective physical planning applications and efficient water management policies are imperative for sustainable hydrological development in this region.