Data sources, licences & attributions

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ERA5 reanalysis — Copernicus Climate Change Service (C3S)

Gridded daily maximum/minimum 2 m temperature (post-processed daily statistics dataset) for June 2026 onwards and the 1991–2020 monthly baselines. Retrieved via the Climate Data Store, 10–12 July 2026, under the Licence to use Copernicus Products. Required acknowledgement:

Contains modified Copernicus Climate Change Service information [2026]. Neither the European Commission nor ECMWF is responsible for any use of this information.

Citation: Hersbach, H. et al. (2020): The ERA5 global reanalysis. Q J R Meteorol Soc. Data via the Copernicus Climate Data Store.

Open-Meteo Historical Weather API

Per-city daily temperature series and 1991–2020 city normals. Retrieved 10–12 July 2026. Licensed CC BY 4.0, free for non-commercial use.

Weather data by Open-Meteo.com

Open-Meteo's historical archive is itself built on ERA5 and national weather model reanalyses.

Region boundaries — Eurostat/GISCO, NUTS 2021

NUTS level-1 statistical regions, 1:20M generalised GeoJSON, retrieved 12 July 2026 from GISCO. Geometry simplified further for the web. Use of these boundaries requires:

© EuroGeographics for the administrative boundaries

Event markers & written analysis

Record values and warning dates summarise public announcements by the Met Office (© Crown copyright, used under the Open Government Licence v3.0), UKHSA (OGL v3.0), Météo-France as reported by international press, and the World Weather Attribution initiative. UK national records are provisional pending Met Office verification.

Software

Map rendering by MapLibre GL JS (BSD-3-Clause). Offline pipeline: Python, xarray (Apache-2.0), DuckDB (MIT), GeoPandas (BSD-3-Clause). Colour scale derived from ColorBrewer RdBu (colorbrewer2.org, Apache-2.0).

This site's full source code and reproducible data pipeline are available in the project repository. No cookies, no analytics, no tracking.