Part of World Meteorological Organization Standard Normals.

WMO data provide the basis for better understanding the climatology of severe weather and extreme events such as tropical cyclones, El Niño, floods, heat waves, cold waves, droughts and other natural hazards, contributing to saving both lives and property, and improving our understanding and monitoring of the climate system and environment. WMO has drawn attention to issues of major concern, such as ozone layer depletion, global warming, climate change and diminishing water resources.

WMO enhances the application of meteorological and hydrological information for the security and well-being of society. Such information is crucial for addressing major challenges such as food security, water resources management, reduction of pollution, decision-making related to the health sector, transport, tourism among others.

WMO provides guidelines to use procedures for analysing climate data for climate change purposes as well as for other applications. This includes, inter-alia, analysis of extremes in a changing climate, the role of climatological normals in a changing climate and climate data homogenisation. Description of processes, methodologies and practices in climatology are provided within a mandatory publication representing the WMO guide to climatological practices.

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.

Footnotes
1 code for missing value
2 code for value > 0.0 but < the smallest unit at the archived precision