Rainfall is often considered as the source of the hydrological cycle. So, being able to forecast rainfall accurately has immense practical benefits. In this book, experts worldwide share their knowledge and highlight challenges on rainfall forecasting. It contains six chapters, they are (1) Statistical downscaling for short term quantitative precipitation forecasting - some achievements and long trail ahead, (2) Empirical approaches in long-term rainfall forecasting, (3) The challenge of warm-season convective precipitation forecasting, (4) The precipitation field in southern Italy: climatology, physical factors and forecasting techniques, (5) Prediction of tropical cyclone rainfall potential in Taiwan mountainous areas, and (6) Real time flood control using quantitative precipitation forecast and ensemble approach.