R package GSODR. Download, clean, reformat and create new variables from the USA National Climatic Data Center (NCDC) Global Surface Summary of the Day (GSOD) weather stations data, <https://data.noaa.gov/dataset/global-surface-summary-of-the-day-gsod>. The function, get_GSOD(), retrieves data from the GSOD ftp site and reformats it from United States Customary System (USCS) units to International System of Units (SI), also for convenience elevation is converted from decimetres to metres. Stations are individually checked for number of missing days, as defined by the user, to assure data quality. Stations with too many missing observations are omitted from final file. Stations with missing latitude or longitude or values for both of 0 are omitted. Also omitted are stations with a latitude of < -90 or > 90 or longitude of < - 180 or > 180. Output is returned as a comma-separated values (CSV) file written to disk in a location selected by the user, which summarises each year by station and includes new variables: actual vapor pressure, saturation vapor pressure and relative humidity, calculated from the original GSOD data. The resulting files can be as large as 500mb depending on the user’s stringency for missing data and geographic area of interest. Be sure to have sufficient RAM and disk space as well as a reasonably fast internet connection to use this package to perform this operation. However, for much smaller and more manageable data sets, an individual country of interest may be selected as well as only stations falling between -60/60 degrees latitude for agroclimatology work or individual stations if the station ID is known. The resulting files include station data (e.g., station name, country, latitude, longitude, elevation) for use in a geographic information system (GIS). The function was largely based on T. Hengl’s ’getGSOD.R’ script, available from <http://spatial-analyst.net/book/system/files/getGSOD.R> with enhancements to be more cross-platform, faster and more flexible. For information on the original data from NCDC, please see the GSOD readme.txt file available from, <http://www1.ncdc.noaa.gov/pub/data/gsod/readme.txt>.