Assessing the Potential of GNSS-Derived Precipitable Water Vapor for Rainfall Prediction and Climate Variability Analysis Abstract Atmospheric water vapor plays a significant role in weather systems, precipitation processes, and the hydrological cycle. Therefore, accurate monitoring of its spatial and temporal variability is essential for both meteorological and climate-related purposes. This study evaluates the potential of Global Navigation Satellite System (GNSS)-derived Precipitable Water Vapor (PWV) for atmospheric moisture monitoring and its applicability as a complementary indicator for short-term rainfall forecasting across different climatic and topographic conditions. The methodology integrates GNSS observations, ERA5 atmospheric reanalysis data, and ground-based precipitation measurements collected from January 2025 to December 2025.