Event Description

In late May 2026, Europe is experiencing an exceptionally intense and unusually early heatwave driven by an atmospheric phenomenon known as a “heat dome“, which was identified as an amplification mechanism for other extreme warm events, like the 2021 North American Pacific Northwest heatwave, which was active for about two weeks  between June and July 2021. This system forms when a persistent area of high pressure traps hot air over a large region, preventing cooler air from entering, inhibiting local convection and precipitation, and allowing temperatures to rise continuously for several days. Lower pressures to the west of the Iberian Peninsula likely also contributed to the high temperatures by advecting warm air from the South. 

The heat dome has expanded across Western and Central Europe, pushing temperatures 10 to 15°C above seasonal averages relative to the 1950-2025 climatology in countries such as France, Germany, Spain, and the United Kingdom. Several cities have recorded their hottest May temperatures ever, with London reaching 34.8°C (hottest May day on the record)  and then experiencing tropical night (with minimum of 21..3°C), while parts of France exceeding 35°C unusually early in the season. This event was particularly remarkable because it immediately followed a period of colder than usual weather earlier in May. These rapid swings between cold and extreme heat are known as “climate whiplash,” a phenomenon becoming increasingly common due to global warming. 

The current heatwave is already affecting public health, infrastructure, agriculture, and energy systems. Authorities across Europe have issued health warnings, especially for elderly people and vulnerable communities, while some regions have experienced water shortages, wildfire risks, and disruptions to outdoor activities. In France, heat alerts were activated the earliest in May since 2004, and officials warned about the dangers of prolonged exposure to extreme temperatures as seven deaths are linked to this record May heatwave.  The UK Health Security Agency issued amber heat-health alerts in many regions of England because older adults, people with cardiovascular and respiratory diseases, and outdoor workers, face elevated risks during prolonged heat exposure, while the hottest May day in the UK could be broken again today (26 May 2026). 

The surface pressure anomalies reveal an anticyclonic anomaly (+10 hPa compared to the 1950–present climatology) 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 continuously warm the surface and near-surface air. 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

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, heatwave frequency has very likely increased in the past decades. The signal has emerged from the natural variability and is attributable to human-induced climate change. An increased trend in heat stress had been detected from 1973 onward. 

Europe is warming faster than the global average, and is expected to continue doing so in the future. In all future scenarios, the frequency of heat extremes will increase, especially in the southern regions. This will increase the disparities within Europe, and extreme heat may exceed critical thresholds for health, agriculture and other sectors more frequently (Chapter 12 WGI IPCC AR6) . At 3 oC of GWL the number of deaths for heat stress will be multiplied by three compared to a 1.5 oC GWL with very high confidence (Chapter 13 WGII IPCC AR6).

Our analysis approach is based on identifying 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 May 2026 have changed in the present (1988–2025) compared to what they would have looked like if they had occurred in the past (1950–1987) in the region [20°W–15°E, 35°N–60°N]. Surface pressure changes show no significant changes over France, while slight increases are observed over the Iberian Peninsula and Western Mediterranean, with values up to +1 hPa, and over the Atlantic (up to +2 hPa). 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 European land areas. These findings are consistent with the long-term warming trend observed in late spring–early summer months across western and central Europe. Wind changes show a slight increase in speed in France, over the eastern North Atlantic off the French and Spanish coasts and over the western Mediterranean, up to +2 km/h. A band of weakened wind speeds appears to the North. 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 March-to-May, compared to a more even distribution between September and November for the past period. This shift supports the interpretation that this heatwave is associated with a circulation feature typical of the transition seasons (Spring and Autumn), and that such extreme heat events are occurring earlier in the season under present-day conditions.

Changes in urban areas show that cities like London, Bordeaux and Paris experienced significantly warmer conditions (up to +1.5  °C) during this event compared to similar past events. Precipitation levels were mostly unchanged, while wind speed changes were minor but slightly positive in all cities.

These results suggest that weather situations similar to those of the May 2026 Western European heatwave are now associated with significantly warmer and locally 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. This corresponds closely with investigations performed on other unprecedented extreme events, like the 2021 North America Pacific heatwave.

Exposure 

We quantify socioeconomic exposure to heat conditions enhanced by climate change by combining event day hazard masks with spatially gridded population and economic data over the study domain used in the meteorological analysis. Population is taken from the Global Human Settlement Layer (GHSL, 2025) and regridded to 0.5° spatial resolution (Schiavina et al., 2022). Economic exposure is estimated using gridded gross domestic product (GDP) per capita data at the same resolution (Kummu et al., 2018). This framework is intended to quantify the spatial coincidence between extreme heat events and socioeconomic assets, rather than to provide an assessment of vulnerability, adaptive capacity, or observed impacts.

The heat hazard is defined from detrended and deseasonalized temperature anomalies during the event and restricted to areas where the ClimaMeter analysis detects a statistically significant positive warming signal in present-day conditions relative to the past. In this way, the exposure estimate focuses on zones where climate change has increased the intensity of the event, albeit with low confidence.

Socioeconomic exposure is calculated by summing the population and economic activity located within each hazard class under present-day conditions.

For the May 2026 European heatwave, the analysis (see Figure) indicates that about 242 million people were exposed to heat conditions intensified by climate change, across areas representing approximately 11,845.00 billion USD of economic activity. Of these totals, 70 million people and 3563 billion USD were in the moderate hazard class, 47 million people and 2396 billion USD in the severe class, and 124 million people and 5885 billion USD in the extreme class. These values highlight that a substantial share of the exposed population and economic assets were located in the highest intensity categories. We remark that these values represent the population and economic activity exposed to the heatwave. They do not represent impacts. For details and limitations about the exposure analysis, the interested reader may consult Faranda et al. (2026).

Conclusion

Based on the above, we conclude that meteorological conditions similar to those causing the May 2026 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 heatwave as an event driven by rare meteorological conditions, whose characteristics are exacerbated by human-driven climate change.