The World Meteorological Organization (WMO) Climatological Standard Normals are a suite of data products that provide information about typical climate conditions for thousands of locations throughout the world. The development and exchange of global climatological normal dates to the early 20th century. Countries around the world (including the United States) produce climate normals that serve as a ruler to compare today’s weather and tomorrow’s forecast, and as a predictor of conditions in the near future. They are also used as a benchmark to provide context to recent or current weather and climate conditions and they provide a basis for many anomaly-based climate datasets. Normals are also widely used, implicitly or explicitly, as a prediction of the to predict the baseline conditions most likely to be experienced in a for specific given locations.
Climatological Standard Normals (1991–2020)
The WMO collected submissions of climatological normals from 141 countries and territories in the six WMO regions*.
- Region I: 30 countries
- Region II: 25
- Region III: 11
- Region IV: 20
- Region V: 13
- Region VI: 42
Each country provided data calculated and digitized in either EXCEL or ASCII *.CSV (comma separated values) format, following the calculation guidance provided in the WMO Guidelines on the Calculation of Climate Normals (WMO-No. 1203) and additional guidelines provided by the WMO (Annex 2).
Additional information on the 1991-2020 WMO Normals is provided in the "Overview" tab. The links below provide access to the Normals data provided by each country in their respective WMO region. Other data including composite files of all data for each of the Primary WMO Normals Parameters are also available.
Station Data Files
- Africa (RA-I)
- Asia (RA-II)
- South America (RA-III)
- North America, Central America and the Caribbean (RA-IV)
- Pacific (RA-V)
- Europe (RA-VI)
*The WMO continues to receive updates and additions from Member countries. The 1991-2020 Normals will be updated to reflect additions and changes in the future.
Composite Data Files and Maps
In addition to the station files provided individually for each country, composite files containing the data for all countries are provided in a CSV file for each of the eight (8) primary parameters. The format of these files is provided in the 1991–2020 Normals readme file.
A set of composite data files for each of the primary parameters also is provided for those Normals values computed with at least 24 years of data in the 30–year period. Parameters for which the number of years were not provided are assumed to have been computed using 30 years of data.
A set of global maps depicting the Normals values for each set of Monthly and Annual Primary parameters also is provided.
Documentation varies by country. Some countries provided extensive information about their Normals calculation methods, but others only submitted data files. In addition, the documentation includes information regarding quality issues identified during the WMO and NCEI data review process.
1991–2020 WMO Normals Overview
The 1991–2020 Climatological Normals are available for a wide variety of elements. Some elements such as temperature and precipitation have global relevance, while others such as snowfall occurrence or temperatures that exceed certain extreme thresholds, only apply to specific parts of the world.
Climatological normals data are provided as values for each month of the year and an annual value. These eight (8) principal elements are the most widely provided by WMO Member countries.
Principal Climatological Elements
- Number of Days with Precipitation greater than or equal to 1 mm
- Mean Daily Maximum Temperature
- Mean Daily Minimum Temperature
- Mean Daily Mean Temperature
- Mean Sea Level Pressure
- Mean Vapor Pressure
- Total Number of Hours of Sunshine
Some countries include additional parameters in their 1991–2020 Normals submissions to support use cases that require more information than the principle elements provide. These can include other aspects of an element’s frequency distribution and statistical behavior, such as the frequency of extended periods when a value is above a threshold (e.g., 25C or 30C). Extreme values of an element over a specified period, and other statistical descriptors of the frequency distribution of an element (such as the standard deviation of daily or monthly values), are also useful descriptors of the climate at a location. Specific examples include:
- Number of days over a specific threshold (such as 25°C)
- Extreme element values over the Normals period (such as highest value of daily maximum temperature)
- Other frequency distribution descriptors (standard deviation of daily or monthly values)
Format and Additional Explanatory Information
Countries submitted their 1991–2020 Normals data in either Excel or Comma Separated Values (CSV) formats. All Excel station files have been converted into individual CSV files (one for each station), so there is one CSV file for every station. Excel files are not available for countries that submitted their Normals data in CSV files. The total number of CSV station files exceeds 6500.
Additional explanatory information specific to the contributions of each country is included in a document for each Region.
The Global Climatological Standard Normals are calculated for a uniform 30-year period, and consist of annual and monthly averages and statistics of temperature, precipitation, and other climatological variables. Since the early 1900s, countries have developed and provided Climatological Standard Normals on a tricennial basis (once every 30 years, e.g. 1901–1930, 1931–1960, 1961–1990). In 2015, the WMO, through the Seventeenth World Meteorological Congress (Cg-17), changed the definition of a Climatological Standard Normal to the most recent 30-year period finishing in a year ending with 0 (1981–2010, 1991–2020 etc) rather than to non-overlapping 30-year-periods (1931–1960, 1961–1990 etc).
NCEI, as host of the World Data Center for Meteorology, and in cooperation with the WMO, provides stewardship of these Global Normals including archive and access services.