High temperatures in the June 2025 Western European heatwave exacerbated by human-driven climate change

Contact Authors

• Davide Faranda, IPSL-CNRS, France,📨davide.faranda@lsce.ipsl.fr, 🗣️English,French, Italian

• Tommaso Alberti, INGV, Italy,📨tommaso.alberti@ingv.it, 🗣️English, Italian

• Carmen Alvarez-Castro, UPO, Spain ,📨mcalvcas@upo.es 🗣️Spanish, English, Italian

• Meriem Krouma, Uppsala University, 📨meriem.krouma@geo.uu.se 🗣️Arabic, French, English

• Valerio Lucarini, University of Leicester, 📨v.lucarini@leicester.ac.uk🗣️Italian, English, French 

Citation

• Faranda, D., Alberti, T., Alvarez-Castro, M. C., & Krouma, M., & Lucarini, V. (2025). High temperatures in the June 2025 Western European heatwave exacerbated by human-driven climate change. ClimaMeter, Institut Pierre Simon Laplace, CNRS. https://doi.org/10.5281/zenodo.15720077

Press Summary

• Meteorological conditions similar to those causing the June 2025 Western European heatwave are up to 2.5 °C warmer and 2 mm/day drier in the present than they were in the past, with surface pressure up to 1 hPa higher and a seasonal shift toward earlier summer occurrences.

• This event was associated with rare meteorological conditions. 

• We ascribe the high temperatures causing the June 2025 Western European Heatwave to human driven climate change and natural climate variability likely played a minor role.

Event Description

From 20 to 22 June 2025, large parts of western and southern Europe experienced an intense early-season heatwave, with Spain,France, UK and Italy particularly affected. In France, the national meteorological agency Météo-France placed 27 departments under yellow alert and 16 under orange alert as temperatures rose rapidly across the country. Central and southwestern regions saw widespread values above 37 °C, with near 40 °C in areas like the Lot and Tarn. This episode marked the 50th heatwave officially recorded in France since 1947, highlighting a concerning acceleration in frequency over the past decades, as reported by Le Monde.

In Spain, the situation was even more extreme. Temperatures exceeded 42 °C in parts of Andalusia and Extremadura, especially near Córdoba (causing the first victim in Spain for extreme temperatures in 2025 as reported by Diario de Córdoba) and Badajoz, with the Spanish State Meteorological Agency issuing red warnings for several provinces. Notably, nighttime minimum temperatures exceeded 25 ºC across most of the country. Likewise, for the 23rd and 24th, AEMET has active orange/yellow warnings in place across a large part of the country. According to AEMET, June 2025 could reach a new record, during a period that also coincided with record-high CO₂ concentrations (430.6 ppm) measured at the Izaña Observatory (Rivas et al, 2025).  This comes on the heels of a heatwave earlier in June, where Mértola in southern Portugal had already reached 40.5 °C. According to AP News, the latest spike led to significant public health concern, with authorities urging people to stay indoors and hydrate during peak afternoon hours (northern Europe bakes in the first heatwave of 2025).

Meanwhile, in the United Kingdom, the heatwave set new records for the year. On 21 June, Charlwood in Surrey reached 33.2 °C, the highest UK temperature so far in 2025. Northern Ireland experienced three consecutive days above 30 °C, meeting the official threshold for a heatwave. Northern England and Scotland, too, saw unusually high values, with Drumnadrochit peaking at 29 °C. The UK Health Security Agency issued an amber heat-health alert, warning of an increased risk of mortality, particularly among older adults and those with pre-existing health conditions. According to The Guardian, early estimates suggest that around 570 excess deaths may have occurred in England and Wales between 19 and 22 June, including 129 in London alone (heatwave likely to kill almost 600 people). Fire Brigades across the country warned of wildfire risk, also exacerbated by the extremely dry conditions - north-west of England having entered official drought status already a month ago. So far, the UK has experienced an increase of wildfires of over 700% with respect to the same period of 2024. 

The surface pressure anomalies reveal an anticyclonic anomaly over central-to-northern Europe, which is closely associated with the persistence of extreme high temperatures across France, Spain, and the British Isles. This high-pressure system inhibited atmospheric mixing and cloud development, allowing solar radiation to accumulate near the surface. The temperature anomalies indicate widespread warm anomalies reaching up to +7 °C compared to the 1950–present climatology. The most intense anomalies are observed over France and northern Spain, extending into southern England, consistent with the observed heatwave conditions. The precipitation data show a marked absence of rainfall over most of western Europe during the event, with the exception of localized convective precipitation in the Alpine region, Northern Italy, and the Pyrenees. This dry pattern reflects the stabilizing influence of the high-pressure system and the lack of moisture advection. The wind speed data show light to moderate winds across the affected regions, with relatively calm conditions over France and the Iberian Peninsula. The strongest wind speeds are concentrated over the Baltic Sea, suggesting limited ventilation over the areas experiencing the highest temperatures.

Climate and Data Background for the Analysis

It is a fact that the intensity and frequency of heatwaves has increased  at the global scale and in 80% of the cases also at the regional scale. It is also a fact that human-induced greenhouse gas forcing is the main driver of this observed trend (Chapter 11 WGI IPCC AR6). In Europe the heatwave frequency has very likely increased in the past decades and the signal has emerged from the natural variability and this is attributable to human induced climate change. An increased trend in heat stress had been detected from 1973 onward and in all future scenarios the frequency of heat extremes will increase, especially in the southern regions. This will exceed critical thresholds for health, agriculture and other sectors (Chapter 12 WGI IPCC AR6).

Warming in Europe will rise faster than the global average and this will increase the disparities within Europe, with negative impacts for the southern regions, with increases in cooling needs and losses in agriculture. At 3 oC of GWL the number of deaths for heat stress will triplicate compared to a 1.5 oC GWL with very high confidence (Chapter 13 WGII IPCC AR6).

Our analysis approach rests on looking for weather situations similar to those of the event of interest having been observed in the past. For this event we have high confidence in the robustness of our approach given the available climate data, as the event is similar to other past events in the data record.

ClimaMeter Analysis 

We analyze here (see Methodology for more details) how events similar to the meteorological conditions leading to the Western European heatwave of 20–22 June 2025 have changed in the present (1987–2023) compared to what they would have looked like if they had occurred in the past (1950–1986) in the region [20°W 15°E 35°N 60°N]. Surface pressure changes show no significant changes over France and Northern Spain, while slight increases are observed over Germany and The Netherlands, with values up to +1 hPa. This suggests that similar heatwave events today are associated with more persistent anticyclonic conditions than in the past. Temperature changes reveal a substantial warming across the entire region, with present-day conditions showing temperatures up to +2.5 °C higher than their historical counterparts. The most pronounced increases are observed over France, the East sector of Great Britain, and northern Spain, where the core of the 2025 heatwave was located. These findings are consistent with the long-term warming trend observed in early summer months across western Europe. Increases over Northern Italy and the Alps favored convection and isolated thunderstorm occurrence. Precipitation changes show a reduction of up to −2 mm/day across large parts of France and the Iberian Peninsula, indicating that similar meteorological conditions now result in drier surface conditions compared to the past. This drying trend is especially evident in regions such as northern Spain, the East and South East of England, including London, and western France, which experienced very limited rainfall during the 2025 event. Wind changes show a slight increase in speed in southern France and over the western Mediterranean, up to +1.5 km/h, but a decrease over much of the UK and northern France. This suggests a shift in the spatial distribution of wind anomalies during comparable events, with parts of southern Europe becoming marginally windier, while northern regions tend to be more stagnant.

Similar past events indicate a clear seasonal shift, with a higher fraction of cases now occurring in June, compared to a more even distribution between June and peaking in July for the 1950–1986 period. This shift supports the interpretation that extreme heat events are occurring earlier in the season under present-day conditions.

Changes in urban areas show that cities like Bordeaux, Madrid, London, and Paris experienced significantly warmer conditions (up to +1,5  °C) during this event compared to similar past events. Precipitation levels were consistently lower, particularly in Bordeaux and Madrid, while wind speed changes were minor but slightly positive in Paris.

These results suggest that weather situations similar to those of the June 2025 Western European heatwave are now associated with significantly warmer and drier conditions than in the past, consistent with the expected influence of anthropogenic climate change. The large-scale atmospheric configuration resembles previous events but is now intensified by background warming, while natural variability appears to have played only a secondary role in shaping the event.

Conclusion

Based on the above, we conclude that meteorological conditions similar to those causing the June 2025 Western European heatwave are up to 2.5 °C warmer and 2 mm/day drier in the present than they were in the past, with surface pressure up to 1 hPa higher and a seasonal shift toward earlier summer occurrences compared to similar past events. We interpret this event as an event driven by rare meteorological conditions, whose characteristics can be ascribed to human driven climate change.