Annual climate indicators and warming trend by city, 1951-2025

Annual climate indicators for 1951-2025 for the largest cities (frost days, hot days, tropical nights, temperature anomaly, warmest-year rank) and the warming trend, computed from the daily ERA5-Land values.

Columns. tmean_c (°C), tmean_anomaly_c (°C), precip_mm (mm), precip_anomaly_pct (%), wet_days, heavy_rain_days, max_1day_precip_mm (mm), frost_days, ice_days, summer_days, hot_days, tropical_nights (days), tmax_abs_c (°C), tmin_abs_c (°C), degree days hdd_15_5, hdd_18, cdd_18, cdd_22 (°C·day), rank_warmest. Trend columns in the cities file: tmean_annual_c, precip_annual_mm, trend_c_per_decade_1951_2025, trend_c_per_decade_1981_2025, warmest_year, coldest_year, wettest_year, driest_year.

Method. Copernicus ERA5-Land hourly reanalysis, 0.1° grid, nearest cell to the city point, local civil days (IANA time zone, complete days only). Temperatures are adjusted for altitude at 6.5 °C per km; precipitation is not adjusted.

Limits. Grid-cell reanalysis values, not station measurements. Daily extremes are smoothed: on record heat days the daily maximum is often 2 to 7 °C below the station record (London, 19 July 2022: 36.4 °C here, 40.2 °C measured at Coningsby). Hot days in city centres are undercounted. Degree days differ from figures published by national services.

Places. France and Germany: the 100 most populous municipalities by official population (France: INSEE population from the "Liste des communes de France" file on data.gouv.fr, Licence Ouverte 2.0; Germany: BKG VG250-EW, © GeoBasis-DE / BKG (2026), dl-de/by-2-0, data changed (climate values added)). One point per municipality (city districts such as the Paris arrondissements are not separate cities); names are the official municipality names; the point and time zone come from GeoNames (cities5000), CC BY 4.0. United Kingdom (100), Portugal (20), Serbia (20) and Luxembourg (5): the most populous GeoNames (cities5000) places, skipping a place that lies in the same 0.1 degree grid cell and district as a larger one. The population column is the official municipal population in France and Germany and the GeoNames population elsewhere; city_id is the GeoNames id. Files are named <cc>_... per country (gb, de, fr, pt, lu, rs).

Attribution. Weatheo (by CODELIO), CC BY 4.0. German names and populations: © GeoBasis-DE / BKG (2026), dl-de/by-2-0, data changed (climate values added). Contains modified Copernicus Climate Change Service information 2026. Neither the European Commission nor ECMWF is responsible for any use that may be made of the Copernicus information or data it contains. Copernicus DEM GLO-90 © DLR e.V. 2010-2014 and © Airbus Defence and Space GmbH 2014-2018 provided under COPERNICUS by the European Union and ESA.

Published by Weatheo. Code (MIT) and build scripts: GitHub repository.