WMO Climate Guide: Global Monthly Observations

Use the WMO Climate Explorer to inspect monthly station observations, compare like calendar months, distinguish observations from anomalies, and export reproducible CSV data.
Author

Climate Explorer Team

Modified

August 3, 2026

Open the WMO Climate Explorer

WMO Climate map view showing Buzău, Romania selected

WMO Climate map centered on Romania showing the selected station Buzău

Quick start

  1. Open the explorer and view the global stations map.
  2. Select a country to filter station choices and center the view.
  3. Choose a specific station to inspect its observations.
  4. Open the Dashboard to inspect monthly time series and the underlying table.
  5. Check gaps and the recent-versus-historical status before exporting CSV data.

1. Introduction

The WMO Climate Explorer is an independent visualization of recent and historical monthly climatological reports (CLIMAT) from the global World Meteorological Organization (WMO) observing network. Unlike static climate normals, these station series are extended as new monthly reports are processed and published by the Deutsche Wetterdienst (DWD).

Climate Explorer is not affiliated with WMO or DWD. DWD’s CLIMAT quality-controlled archive is authoritative for the files used by the application.

4. Parameter Definitions

The dashboard maps and exports the following WMO monthly parameters:

Variable Definition Unit
Mean Temperature Monthly mean air temperature reported for the station °C
Max Temperature Reported absolute maximum temperature in the month °C
Min Temperature Reported absolute minimum temperature in the month °C
Mean daily max Average of all daily maximum temperatures in the month °C
Mean daily min Average of all daily minimum temperatures in the month °C
Precipitation Total accumulated rainfall and snowfall mm
Precipitation Days Number of days with precipitation ≥ 1.0 mm days
Sea Level Pressure Average monthly atmospheric pressure at sea level hPa
Vapour Pressure Average atmospheric moisture content hPa
Sunshine Duration Total hours of bright sunshine hours

5. Worked example: a calendar-month comparison at Buzău

The purpose of this example is to compare like with like and to keep the calculation reproducible.

  1. Choose Romania in Select Country.
  2. Choose Buzau (WMO ID 15350) in Select Station.
  3. Open Dashboard → Plots and inspect mean temperature.
  4. Compare July values across selected years. Do not compare July directly with winter months and call the difference a climate anomaly; that would mix the annual cycle with interannual variability.
  5. Open Dashboard → Data and confirm that each selected July has a reported value.
  6. Download the CSV and retain 15350, the variable name, the selected years and the download date in your analysis notes.

To calculate a July temperature anomaly, pair the observation with a July reference value for the same or demonstrably equivalent site. Use the WMO Normals Explorer for 1991–2020 station normals and consult the WMO Normals guide before matching identifiers.

6. A climatologist’s interpretation workflow

Start with the scale of the evidence

Each row is a monthly summary for one station. It can document conditions at that observing point; it does not by itself represent a city, country or the globe. Generalization requires additional stations or an appropriate gridded product.

Distinguish observation, anomaly and trend

  • Observation: the reported monthly value shown in the explorer.
  • Anomaly: the observation minus a named reference value for the same variable and calendar month.
  • Trend: a statistical change through time evaluated after addressing gaps, seasonality, station history and the intended uncertainty model.

The explorer displays observations. It does not automatically calculate an anomaly or establish a trend.

Check completeness before calculation

Review the Data tab for missing months and variables. A blank cell is missing information, not zero. For precipitation, a missing total must not be converted into a dry month. For comparisons across decades, use a consistent set of calendar months so changes in seasonal coverage do not create a false signal.

Treat recent values as revisable

DWD maintains separate recent and versioned historical files. DWD describes recent data as preliminary quality controlled, while historical data have completed routine quality control. The explorer combines the available records for convenience; document the retrieval date and recheck a recent value before publication.

Review station history

Relocation, instrumentation, observing practice and changes in the local environment can introduce discontinuities. A visually smooth plot is not evidence that the record is homogeneous. Consult available station metadata and use a homogenized dataset when the research question requires a formal long-term trend.

7. Data sourcing, processing and quality control

Data is sourced from the DWD CDC Global CLIMAT Observations archive. The application retrieves each displayed parameter from its own DWD directory, parses the year-by-month tables, merges parameters by month and removes duplicate dates where recent and historical files overlap. Missing DWD values remain missing in the displayed series and CSV export.

CLIMAT reports originate with National Meteorological and Hydrological Services. DWD publishes preliminary quality-controlled data under recent and routine-quality-controlled, versioned series under historical. Reporting completeness, record length and variable availability differ by station.