The list of all the WMO's Databases. WMO defines climatological standard normals as "averages of climatological data computed for the following consecutive periods of 30 years: January 1, 1901 to December 31, 1930, January 1, 1931 to December 31, 1960, etc." (WMO, 1984).The latest global standard normals period is 1961-1990. The next standard normals periode is January 1991 – December 2020.