GRASS GIS is a general purpose Free and Open Source geographic information system (GIS) that offers raster, 3D raster and vector data processing support. In this session we will start with a few GRASS GIS basics, showing its concepts. We then focus on analysing the ECA&D data which is a European climatic data time series of daily temporal resolution. Using it we look at the data organization and perform data aggregation in GRASS GIS, along with univariate statistics, raster map algebra, and zonal statistics. This part is followed by classification with machine learning (RandomForest Classifier) and concluded with a quick glance at linear and multiple regression in GRASS GIS.