The effective use of climate data and products requires an understanding of what the statistical parameters mean and which parameters best summarize the data for particular climate variables. This lesson addresses both concerns, taking a two-pronged approach: 1) focusing on the statistical parameters (mean, median, mode, extreme values, percent frequency of occurrence and time, range, standard deviation, and data anomalies), defining what they mean and how they are calculated using climate data as examples, and 2) focusing on weather and climate variables, identifying the statistical parameters that best represent each one. The lesson concludes with a discussion of data quality and its impact on weather and climate products. The lesson is intended for forecasters and others interested in improving their understanding of the basic statistics used in climate products so they can make better use of climatology products for planning and operational purposes. Basic knowledge of meteorology is beneficial although not required. This lesson is part of COMET’s Climatology for Forecasters series.