NOAA GHCNm – Global Monthly Data

Explore NOAA/NCEI GHCNm monthly temperature and precipitation records in an independent interface covering land stations worldwide.

NOAA GHCNm overview

Climate Explorer provides an independent interface for the NOAA/NCEI GHCNm global monthly archive. Climate Explorer is not affiliated with NOAA. This Explorer is designed for viewing long monthly station histories, comparing one calendar month across years, and inspecting descriptive station-level trends.

NOAA/NCEI maintains, curates, quality-controls, and publishes the GHCNm archive using observations from contributing national and international meteorological networks. Climate Explorer retrieves, parses, and presents those records; NOAA/NCEI remains the authoritative source for the archive and its documentation.

Pro Tip

Click the Maximize button in the top-right corner of the explorer frame to expand to Full Screen mode for optimal map and chart visibility. Click it again or press Esc to exit.

Dataset facts

Official source
NOAA National Centers for Environmental Information GHCNm.
Coverage
Land stations worldwide; the earliest records reach into the 18th century, but start dates, end dates, variables, and completeness differ by station.
Update frequency
Operational records are updated on NOAA release schedules; precipitation is typically refreshed monthly.
Licence
CC0 1.0 Universal Public Domain Dedication; retain NOAA/NCEI attribution and source metadata.
Important limitation
The Explorer serves NOAA’s adjusted qcf monthly mean temperature—not unadjusted temperature or monthly minimum/maximum—and NOAA’s beta v4 precipitation product. Station periods and completeness differ.
Worldwide station coverage

GHCNm combines land-station records contributed through numerous national and international sources. Coverage is broad but not uniform: confirm that the requested country, station, variable, month, and period are present before beginning an analysis.

What the Explorer currently serves

  • Temperature: NOAA GHCNm v4 monthly mean temperature (TAVG) from the quality-controlled, adjusted qcf archive, displayed in °C. NOAA applies the Pairwise Homogenization Algorithm (PHA) to this product.
  • Precipitation: NOAA GHCNm v4 monthly precipitation totals, displayed in mm. NOAA currently identifies this as a beta product; unlike the temperature data, it is not adjusted using the Pairwise Homogenization Algorithm (PHA).
  • Station context: Name, GHCNm identifier, country, coordinates, elevation where available, and record span.
  • Selection context: One parameter, one calendar month, and one year range at a time.

The map color represents the mean of the available values for the selected calendar month and year range. After selecting a station, the panel shows the annual sequence for that month, a linear fit, its slope, and the mean. Missing years are not zero, and the fitted line does not by itself provide statistical significance, causal attribution, or regional representativeness.

Appropriate uses and limits

The Explorer is useful for locating long station histories, comparing like-for-like calendar months, and making an initial inspection of a local temperature or precipitation trend. It is not designed to resolve individual storms, heat spikes, or other short-duration events. For hourly event analysis, use the GHCNh Explorer or another higher-frequency source.

For temperature, the interface does not currently expose NOAA’s quality-controlled unadjusted qcu product or monthly minimum/maximum series. Users who need an adjustment comparison must retrieve qcu from NOAA and document that external step. The GHCNm download and interpretation guide explains the served fields, CSV export, quality checks, and a reproducible station-trend workflow. The companion article explains what a GHCNm station trend can—and cannot—show.

Data source and code

Source material and citation

  • Official NOAA documentation for the dataset is available through the NCEI GHCNm landing page.
  • When referencing results, cite NOAA/NCEI as the data originator and include the Climate Explorer URL so readers can reproduce the visualization workflow.
  • For methodology details, consult the v4 technical note and quality-control addenda included on the official download page.

Frequently Asked Questions

What is the GHCNm dataset?

The Global Historical Climatology Network Monthly (GHCNm) is a NOAA/NCEI archive of monthly mean temperature and monthly precipitation records from thousands of land stations worldwide.

Why use monthly data instead of daily or hourly?

Monthly data summarizes conditions at a coarser time scale than daily or hourly observations. It is useful for seasonal and multi-decadal comparisons, but it cannot resolve the timing of short-duration weather events.

Are the Explorer’s records homogenized?

The Explorer serves NOAA’s adjusted qcf monthly mean temperature product, to which NOAA applies PHA. It does not serve unadjusted qcu temperature. The precipitation series is a separate product and is not PHA-adjusted. Adjustments reduce identified discontinuities but do not guarantee that every non-climatic influence is removed.

How often is the GHCNm data updated?

NOAA/NCEI publishes operational releases on its own schedules. The Explorer displays the newest temperature and precipitation month currently loaded into the application; it may lag a newer NOAA release.

How do I analyze long-term climate trends?

Choose a parameter, calendar month, and year range, then click a station. The panel displays the available values and a descriptive linear fit for that selection. Check gaps, flags, sensitivity to the time window, neighboring stations, and—when relevant—NOAA’s external unadjusted temperature product before drawing a broader conclusion.

Does Climate Explorer produce the GHCNm records?

No. Climate Explorer is an independent interface and is not affiliated with NOAA. NOAA/NCEI maintains, curates, quality-controls, and publishes the GHCNm archive using observations from contributing meteorological networks; Climate Explorer retrieves, parses, and presents those records.