Typical Global Climate Conditions

In cooperation with the World Meteorological Organization (WMO), NCEI’s World Data Center for Meteorology has released a collection of 1991–2020 Climatological Standard Normals from 141 countries and territories. These normals make up a suite of data products that provide information about the typical climate conditions of thousands of locations throughout the world. Countries on every continent produce Climate Normals that collectively serve as a ruler for comparing today’s weather with tomorrow’s forecast, as well as a predictor of conditions in the near future. Climate Normals are also used as a benchmark to provide context to recent or current weather and climate conditions and are widely used, be it implicitly or explicitly, to predict the baseline conditions most likely to occur in specific locations.

What are WMO Normals?

The 1991–2020 WMO Normals, produced by each country and submitted to the World Meteorological Organization, contain the average monthly and annual climatological conditions of more than 6,600 locations across all continents. 

This dataset contains eight Principal Parameters:

• Precipitation
• 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

NCEI provides these data in “Comma-Separated Value files” for each station as well as in sets of eight composite files—one for each Principle Parameter—that contain all the Normals data provided for the respective parameter.

Figure 1 provides an example of the Normal precipitation for the month of July. Climatologically drier locations include areas such as the western U.S., the Mediterranean countries of Europe and North Africa, coastal areas of Peru, large parts of Brazil and northern Argentina, much of Southwest Asia, and large parts of Australia. Among the climatologically wettest areas in July are West Africa, much of India, Bangladesh, and Southeast Asia, eastern China, northern parts of South America, Central America, the Caribbean, and parts of the eastern U.S.

Typical July conditions contrast sharply with typical January conditions (Figure 2) in many places. For instance, many parts of India and Bangladesh that receive more than 250 mm (~10 inches) in July receive little to no precipitation in January. In contrast, large parts of Brazil that receive little precipitation in July typically receive more than 100 mm (~4 inches) in January.

Criteria for Datasets

Some countries included additional parameters in their 1991–2020 Normals submissions to support use cases that require more information than the principle elements provide. These are included in the individual station-specific CSV files. They incorporate 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., 25°C or 30°C). Extreme values of an element over a specified period, as well as 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 (such as the standard deviation of daily or monthly values).

The 1991–2020 WMO Normals include maps and composite files for all Principal Parameters—they are available on NCEI’s website.