Given the fact that rainfall is an integral product of the raindrop size distribution (RSD), hydrological models are sensitive to the variability of the RSD. In this study, we determined the characteristics of raindrop size distribution for given storms in Greater Houston, Texas and in Orlando, Florida and the storms RSD characteristics were linked to weather systems utilizing synoptic charts and radar animation. The RSD characteristics include the distribution of small, midsize, and larger drops that were determined through time series of RSD based on disdrometer measurements, while the weather systems include tropical cyclones, frontal systems, and sea-breeze convection. In addition, mesoscale convective systems and upper level disturbances were observed in Houston. The purpose of this study was two fold: First, to derive the RSD parameters for each system, an input for cloud models. Second, to determine the radar rainfall relations for each system. While the first objective is related to the improvement of the microwave rainfall retrieval algorithm that employs cloud models as an input, the improvement of quantitative precipitation estimation and forecast highly depends on the radar rainfall relation. As stated above, both objectives have multidisciplinary applications in hydrology, meteorology as well as in agricultural and soil sciences.