Event Description

Beginning in late June 2026, Europe experienced an exceptionally intense and record-breaking heatwave driven by an atmospheric phenomenon known as a “heat dome”. Such a heat dome is associated with a stable atmospheric blocking pattern that inhibits the typical west-to-east progression of weather systems. This persistent blocking high-pressure system, in this case organised as an “Omega block”, has been identified as an amplification mechanism for other extreme warm events, such as the 2021 North American Pacific Northwest heatwave (White et al. 2023). 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, cloud formation, and precipitation, and allowing temperatures to rise continuously for several days. A surface low-pressure system to the west of the Iberian Peninsula also contributed to the high temperatures by advecting warm, dry air from North Africa towards Western Europe.

The heat dome expanded across Western, Central and, by the end of the period, Eastern Europe, pushing temperatures 5 to 12 °C above seasonal averages in countries such as France, Germany, Spain, Italy, Poland and the United Kingdom. Several countries recorded their hottest June — and in some cases all-time — temperatures: France reached its hottest June day on record (43.3°C), with 49 of 96 mainland departments placed under the top (red) heat warning. Paris-Montsouris exceeded 40°C on two consecutive days in June 2026 — more >40°C days than had been recorded there in the first 147 years of observations, before the 2019 heatwave. The United Kingdom set a new June record of 37.7°C in Lingwood  surpassing the 35.6 °C of 1976; Germany set a provisional national record of 41.7°C in Brandenburg on the 28th June, after also setting national records above 41°C on the 26th and 27th June ; the 105 year old national record fell in Poland (40.5°C in Słubice), the all time temperature record fell in Hungary (preliminary 42.0°C at Szécsény), Slovakia set a new all-time record of 41.3°C near the Hungarian border, and all-time or June records also fell in Spain, where temperatures reached 45.1 °C in Andújar (Jaén) on 23 June, among the highest values observed during the event; and Portugal (up to ~44 °C), the Czech Republic (40.6 °C at Doksany), Denmark (all time high temperature of 37.0 °C), Croatia (all time records set in several locations such as Split)and Switzerland (June temperature record of 38.8°C). The peak in Western Europe occurred between 20 and 23 June. Night-time temperatures were also exceptionally high. The nights of 22 and 23 June were the warmest June nights on record in Spain since at least 1950, with little overnight relief from the heat. In the United Kingdom, the minimum temperature remained as high as 23.5 °C in Cardiff, setting a new national June night-time record on 25 June, highlighting the persistence of the heat across western Europe. The event also set records directly relevant to heat stress: WMO reported that overnight temperature records tumbled, including a 29.4°C minimum in East Saxony, the hottest ever night in Germany (by two degrees) and possibly the hottest night ever recorded above 50 degrees latitude. DWD termed the heatwave as “historic”. Temperatures dropped below red alerts on June 28th.

This event was particularly remarkable because it followed only weeks after an exceptionally early May heatwave that had already broken spring records. A rapid attribution analysis by World Weather Attribution described the event as the most severe heatwave ever recorded over the region, concluding that comparable June heat would have been “virtually impossible” in 1976 and that night-time temperatures such as those observed are now more than a hundred times more likely than they were in 2003 (Keeping et al., 2026).

The heatwave severely affected public health, infrastructure, agriculture and energy systems. By 28 June, the World Health Organization linked more than 1,300 excess deaths across Europe to the event, with France reporting around 1,000 excess deaths — mostly among people over 65 — and Spain registering 327 heat-attributed deaths. We underline that this balance is still provisional, and a preprint study using peer-reviewed methods currently estimates 20,000 deaths across the continent (Callahan 2026). Authorities issued red and amber heat-health alerts; France closed hundreds of schools; rail operators (including Deutsche Bahn) advised against non-essential travel as buckling tracks and split asphalt disrupted transport; a hospital in the UK declared a critical incident; and energy systems came under strain, with cooling demand at multi-decade highs and concerns over reduced output from French nuclear plants cooled by the Rhône and Garonne rivers. Wildfire red alerts were issued across France, Iberia and parts of Central Europe.

The surface-pressure anomalies (relative to the 1950–present climatology) reveal a strong anticyclonic anomaly of up to +5 to +7 hPa over Central-to-Northern Europe, closely associated with the persistence of extreme temperatures across France, the British Isles and Central Europe, together with a negative anomaly of −5 to −7 hPa over the eastern North Atlantic west of Iberia. The temperature anomalies indicate widespread warm anomalies reaching up to +10 to +12 °C, most intense over France and extending into Spain, the Netherlands and southern England. The precipitation data show a marked absence of rainfall over most of Western Europe, with only localised convective precipitation over the Alps, Northern Italy and the Pyrenees, reflecting the stabilising influence of the high-pressure system and the lack of moisture advection. The wind-speed data show light to moderate winds over France and the Iberian Peninsula, with the strongest winds confined to the Atlantic and the Bay of Biscay, indicating 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 cases, also at the regional scale. It is also well established 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. An increased trend in heat stress has 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 southern regions. This will increase 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 °C of Global Warming Level (GWL), the number of deaths from heat stress will be multiplied by three compared with a 1.5 °C GWL, with very high confidence (Chapter 13: Europe, 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, which is why the event is classified as a rare — rather than a very exceptional — meteorological event.

ClimaMeter Analysis 

We analyse here (see Methodology for more details) how events similar to the meteorological conditions leading to the European heatwave of 21–27 June 2026 have changed in the present (1988–2025) compared with 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 a dipole pattern, with a slight increase over North-Eastern Europe (up to +1 hPa) and a weakening of pressure over the eastern North Atlantic and the Bay of Biscay (down to −1 hPa), indicating a modest north-eastward shift of the blocking configuration. 

Temperature changes reveal a substantial warming across the entire region, with present-day conditions up to +2.5 °C warmer than their historical counterparts; the most pronounced increases occur over European land areas, consistent with the long-term early-summer warming trend across Western and Central Europe. Precipitation changes are spatially heterogeneous, with present-day drying over parts of France and the Iberian Peninsula and localised wetting elsewhere. Wind changes show a general weakening over the western North Atlantic, pointing towards more stagnant conditions during comparable events — a configuration that favours high near-surface temperatures.

The persistence of analogous conditions similar to the meteorological conditions leading to the European heatwave of 21–27 June 2026 has increased in the present period (see supplementary figure), meaning that such heat-dome configurations now tend to last longer.  Similar past events indicate a seasonal shift: a higher fraction of cases now occurs in late summer, peaking in August, compared with a more even distribution across June–September in the past period. This supports the interpretation that such extreme heat events are increasingly associated with the warmest part of the summer under present-day conditions, notwithstanding the fact that the current heatwave occurred in June.

Regarding the role of large-scale natural variability, both the Atlantic Multidecadal Oscillation (AMO) and the Pacific Decadal Oscillation  likely affect similar events in the present. The significantly more positive AMO phase associated with present-day analogues, linked to a warmer North Atlantic, indicates that part of the shift in analogue selection reflects a change in the natural background state, which is why the attribution gauge is positioned in the mixed regime between natural variability and climate change. Crucially, however, this multidecadal modulation acts primarily on the large-scale circulation and on the selection of analogues, rather than on the thermodynamics of the warming itself. Accordingly, the large-scale, spatially coherent warming signal in 2-meters temperature observed between past and present analogues remains robust across all sensitivity configurations and can be interpreted as evidence of thermodynamic amplification driven by anthropogenic climate change.

Changes in urban areas show that cities such as Toulouse (up to +2.2 °C) and Paris and London (up to +1.5 °C) experienced significantly warmer conditions during this event compared with similar past events. Precipitation changes were minor and slightly negative, while wind-speed changes were small and slightly negative across the three cities. These results suggest that weather situations similar to those of the June 2026 European heatwave are now associated with significantly warmer, more persistent and locally drier and more stagnant conditions than in the past. The large-scale atmospheric pattern resembles previous events but is now intensified both by anthropogenic background warming and by a more positive phase of Atlantic multidecadal variability. 

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 deseasonalised 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 approximately reflects zones where climate change has increased the intensity of the event. We define three mutually exclusive hazard classes, moderate, severe and extreme, according to the local percentile of the event-day temperature anomaly: the moderate class collects the grid points falling between the 98th and 99th percentiles, the severe class those between the 99th and 99.5th percentiles, and the extreme class those exceeding the 99.5th percentile of the local reference distribution. Socioeconomic exposure is calculated by summing the population and economic activity located within each hazard class under present-day conditions.

For the June 2026 European heatwave, the analysis (see Figure) indicates that between 21st and 27th June about 327 million people were exposed to heat conditions intensified by climate change, across areas representing approximately 15,618 trillion USD of economic activity. Of these totals, 29 million people and 884 billion USD were in the moderate hazard class, 34 million people and 1,366 billion USD in the severe class, and 264 million people and 13.4 trillion USD in the extreme class. These values highlight that the overwhelming majority of the exposed population (about 81%) and of the exposed economic assets (about 86%) were located in the highest-intensity category, an even stronger concentration in the extreme class than observed for comparable past events. 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 June 2026 European heatwave are up to 2.5 °C warmer in the present than they were in the past (1950-1987), with locally drier and more stagnant conditions, a significant increase in the persistence of such configurations, and a seasonal shift toward the warmest part of the summer (August). While natural variability modulates the large-scale circulation and the selection of analogues, the underlying warming signal is large-scale, spatially coherent and robust. We therefore interpret this heatwave as an event driven by rare meteorological conditions whose intensity has been substantially exacerbated by human-driven climate change, through the thermodynamic amplification of temperatures under an otherwise recurrent atmospheric configuration.

Additional Information : Complete Output of the Analysis

NB1: The following output is specifically intended for scientists and contain details that are fully understandable only by reading the methodology described in Faranda, D., Bourdin, S., Ginesta, M., Krouma, M., Noyelle, R., Pons, F., Yiou, P., and Messori, G.: A climate-change attribution retrospective of some impactful weather extremes of 2021, Weather Clim. Dynam., 3, 1311–1340, https://doi.org/10.5194/wcd-3-1311-2022, 2022. 

NB2: Colorscales may vary from the ClimaMeter figure presented above.