How to Use WMO Normals: Station Charts and CSV Export

Select a WMO 1991–2020 normals station, compare monthly values, read the dashboard correctly, and export all available station parameters to CSV.

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Open the WMO Normals Explorer

WMO Normals Explorer map showing 1991–2020 climate stations worldwide

Quick start

1. Choose a parameter and month or Annual in the sidebar.
2. Choose a country, then select a station or click its map point.
3. Read the station’s monthly matrix and available charts in Dashboard.
4. Select Export CSV to download every available primary parameter for that station.

Choose the right workflow

Use the WMO Normals Explorer when you want to browse or compare station baselines. This guide covers the repeatable station and download workflow. If your question is whether normals describe current climate, trends or extremes, read The Limits of WMO Normals in a Warming Climate before interpreting the result.

1. Set the map variable and time period

The map uses two controls together:

• Select Parameter chooses one of eight layers: mean, maximum or minimum temperature; precipitation; precipitation days of at least 1 mm; mean sea-level pressure; mean vapor pressure; or sunshine duration.
• Select Time Period chooses Annual or one calendar month.

Changing either control changes the values and the eligible station set on the map. A missing point does not necessarily mean that the station is absent from the WMO archive; it may not have a usable value for that particular parameter and period.

2. Find and open a station

Choose a country to narrow the station list and zoom the map. Then either:

• choose a station from Select Station, or
• click a coloured station point on the map.

Both routes open the Dashboard. The header identifies the station name, country, legacy WMO ID, coordinates and elevation used by the Explorer. Record the ID when you need to reproduce or audit a selection; station names are not always unique.

• Full Screen View: Click the Maximize / Full Screen button in the top-right corner of the explorer window to expand the dashboard to full display size. This is recommended when inspecting complex multi-panel charts, high-density station maps, or large data tables. Press Esc or click the icon again to exit.

Worked example: Bremen

1. Set Select Parameter to Mean Temperature and Select Time Period to Annual.
2. Choose Germany under Select Country.
3. Choose Bremen under Select Station.
4. Confirm that the Dashboard header shows legacy WMO ID 10224.
5. In the matrix, compare the June mean-temperature normal with the annual mean, then inspect the temperature and Walter–Lieth charts.
6. Select Export CSV and confirm that the filename contains 10224.

The screenshot below shows this station dashboard. Its contents are a fixed 1991–2020 reference, not current Bremen weather.

WMO Normals dashboard for Bremen showing station metadata, a monthly matrix and seasonal charts

3. Read the station matrix

The matrix has one row per available parameter and columns for January through December plus Annual. Blank or absent rows mean that the primary composite has no usable value for that station.

How monthly and annual WMO Normals matrix values should be read

Explorer row	Monthly value	Annual value	Unit
Mean, maximum or minimum temperature	Average for that calendar month over 1991–2020	Annual average	°C
Precipitation	Average total for that calendar month	Annual total	mm
Precipitation Days (≥1 mm)	Average count for that calendar month	Annual count	days
Mean Sea Level Pressure	Monthly average	Annual average	hPa
Mean Vapor Pressure	Monthly average	Annual average	hPa
Sunshine Duration	Average total hours for that calendar month	Annual total	hours

Do not compare a temperature average directly with a precipitation total, or treat the Annual column as one universal calculation. Always keep the row definition and unit attached to the number.

4. Use the charts without over-reading them

The dashboard creates only the charts supported by the selected station’s available parameters:

• Walter–Lieth diagram places mean temperature and precipitation on a shared seasonal chart; its scaling is intended to show relative humid and arid periods, not to convert rainfall into temperature.
• Temperature curves compare monthly mean maximum, mean and minimum temperature.
• Precipitation, precipitation days, pressure, vapor pressure and sunshine panels show the annual cycle for their respective variables.

These plots describe the 1991–2020 baseline. They do not show individual years, post-2020 observations, trends, forecasts or record extremes.

5. Export a station CSV

After a station is open in the Dashboard:

1. Select Export CSV in the station header.
2. Save the file named WMO_Normals_1991-2020_<WMO-ID>.csv.
3. Confirm that the first column is Parameter and the remaining columns run from Jan through Dec and Annual.
4. Keep blank cells as missing values. Do not replace them with zero.
5. Store the station name, WMO ID, reference period and access date with your analysis.

The export combines every primary parameter available for the selected station, not only the parameter that was active on the map.

6. Compare two stations safely

For a defensible comparison:

1. Use the same parameter, month and unit for both stations.
2. Record each station’s WMO ID, coordinates and elevation.
3. Check whether both values come from the same 1991–2020 reference period.
4. Note differences in altitude, coast proximity, urban setting and exposure.
5. Treat the result as a point-to-point station comparison, not automatically as a city, national or regional comparison.

If you combine a normal with observations, match the same station identity and compatible variable. For example, a June WMO mean daily maximum is not the same measure as one instantaneous temperature observation. See the European capitals comparison for a worked example with that limitation stated explicitly.

7. Troubleshooting

• The station list is shorter than expected: The list follows the selected parameter. Try another parameter or choose All Countries.
• Changing the parameter returns to the map: This is expected. The app clears the active Dashboard selection so the map can show the new eligible station set.
• A dashboard row or chart is missing: That parameter is not available for the selected station in the Explorer’s primary composite tables.
• The annual value looks inconsistent with the months: Check whether the variable is an average, total or count. Do not recalculate an annual field without consulting the source documentation.
• Two nearby stations differ: Verify their IDs, coordinates, elevation and setting. Nearby does not mean climatologically interchangeable.
• You need recent weather or a trend: Use EuroMeteo observations for recent European station data or the GHCNm guide for long monthly temperature series.

8. Official source and data threshold

WMO Members calculate and submit the normals. NOAA NCEI archives the global collection and publishes eight primary-parameter composites. The Explorer uses the composite variants containing normals computed with at least 24 years of data in the 30-year period; where the number of years was not supplied, NCEI states that 30 years is assumed.

Methods and documentation can still vary by country. Consult the NOAA NCEI WMO Climate Normals documentation and the WMO Guidelines on the Calculation of Climate Normals when calculation details matter.