The uses for geographic information systems (GIS) and statistical software in hydrology and meteorology are unlimited. The application of GIS in hydrology includes terrain analyses, basin boundary delineation, model parameter estimation, data visualization, analysis of meteorological inputs to models, such as radar-derived precipitation estimates and snow pack accumulation, illustrates a few uses. More often than not, however, commercial GIS packages are used for these purposes. This paper presents the benefits of using free, open source GIS and statistical software that are often over-looked by hydrologists and meteorologists, both in research, and in operations. Specifically, applications of the Geographic Resources Analysis Support System (GRASS) GIS and R to hydrometeorological problems are presented. GRASS GIS was originally developed by the U.S. Army Corps of Engineers and is now found within the Open Source Geospatial Foundation umbrella of open source projects, and R is found in the R Project for Statistical Computing. Both software packages, as well as other open source software, are used routinely by the National Weather Service, Ohio River Forecast Center (OHRFC) within the Advanced Weather Interactive Processing System (AWIPS). Examples of the use of GRASS GIS and R working together are also presented.