The direct answer
Prepare one month column and one numeric temperature column per city. This wide table fits Datamon’s Heatmap mapping. A long table with repeated months and a city label needs pivoting before import.
Prepare the observation table
Calculate each city’s monthly mean from its 2023 local daily series. Pivot to month, seoul_c, jakarta_c and singapore_c, then map month to X and all three temperature columns to Y. Use a common Celsius color scale and preserve calendar order.
Public dataset and a reproducible example
The download is a prepared extract, not a live data connection. The source links below include the original query, observation period and reuse policy. Keep an original copy when you update the data; revised source values can change the result.
Weather data by Open-Meteo.com, using ERA5 reanalysis; attribution under CC BY 4.0. These are grid-cell estimates with local calendar dates, not station observations or forecasts. Review API terms before automating commercial retrieval.
Snapshot retrieved: 2026-10-26. Prepared rows: 12.
Download the prepared CSVDownload the reference SVG
| month | seoul_c | jakarta_c | singapore_c |
|---|---|---|---|
| 2023-01 | -1.9935 | 26.8903 | 26.0323 |
| 2023-02 | 1.3071 | 26.35 | 26.3393 |
| 2023-03 | 8.6935 | 26.8258 | 26.4097 |
| 2023-04 | 13.4133 | 27.7633 | 27.5867 |
| 2023-05 | 18.7774 | 28.1 | 28.3871 |
Build it in Datamon
Sign in with Google to create an editable visualization. Public articles and examples can be read without an account. The prepared CSV already contains the joins, filters or aggregations described above; do those steps in a spreadsheet first when using your own data.
- Open Data and choose a file, or paste the table with its header row. Check the detected numeric columns, decimal separator and dates. The current importer accepts files below 20 MB; these examples are smaller. Keep blanks distinct from recorded zeros.
- In Visualize, select Heatmap. Connect the roles exactly as listed below. Review the preview against at least two rows in the example table rather than relying only on automatic mapping.
- In Refine, add a title that states the question, the unit, observation period and source. Check labels and contrast at the size your reader will see. Keep a table when exact values matter.
- Use the export controls for SVG, PNG, PDF or PowerPoint, then inspect the actual file. Save an editable project backup. Publish only after checking the underlying values: a public link makes the published data available to anyone possessing the URL.
Calculation and column mapping
The rule below is pseudocode. The downloadable CSV already contains the prepared values; spreadsheet functions and cell references depend on your sheet layout.
MEAN daily temperature by local month, then pivot city to numeric columns- X
- month
- Y
- seoul_c, jakarta_c, singapore_c
Read the result
In this extract, seoul_c ranges from -1.994 (2023-01) to 26.91 (2023-08).
Use the preview to check the structure and the CSV to check exact values. Its styling is a reference; your Datamon rendering can look different. Follow the mapping and preparation above to reproduce the analytical meaning.
Mistakes that change the meaning
The color scale shows temperature levels, not deviations from each city’s own climate. To compare unusually hot months, compute city-specific anomalies using a documented multiyear reference; a single year cannot supply that climatology.
Questions before sharing
Do these calculations require an AI service?
No. The prepared CSV and reference calculation are deterministic. Optional AI can help draft an explanation when configured, but it does not replace checking source values or choosing a valid comparison.
Can I use this example with my own spreadsheet?
Yes. Keep the same observation unit, column types and calculation. Replace the source attribution and time period, recompute derived columns, then compare several output values with your original sheet before sharing.
What is free and what needs an account?
Reading this guide and downloading its CSV and chart images are free. Datamon currently has no paid checkout or subscription plans in this deployment. Creating and saving an editable visualization requires Google sign-in. Provider-backed AI, cloud analysis, publishing and video depend on configured services; this guide does not promise unlimited free connected services.
Sources and further reading
Report a correction or an access barrier: Email the editorial contact.
Open Datamon