Until now, Europe’s 2026 heatwaves have been produced by recognisable weather patterns. What has made them exceptional is the warmer climate in which those patterns now operate.

Europe didn’t have to wait until August for serious summer heat. By late May, temperatures in parts of western France, England and Wales were already more than 10°C above their recent seasonal average. A record-breaking June followed, and the heat will continue into July.

What counts as a heatwave?

A heatwave isn’t defined by one universal temperature. It’s a sustained period of unusually hot conditions relative to what’s normal for a particular place and time of year. National warning systems may also consider nighttime temperatures, humidity and expected health effects.

That local context matters. A temperature regularly experienced in inland Andalusia may constitute a severe anomaly in Denmark, where residents, buildings and infrastructure are adapted to a cooler climate. Heat risk therefore depends on the temperature itself, and how unusual it is and how prepared the affected population is.

A summer that began in May

The first major episode occurred mainly between 21 and 30 May. Portugal, the United Kingdom and Ireland provisionally recorded their highest May temperatures, while France experienced its hottest May day nationally. Its early timing was important: people had little opportunity to acclimatise, while schools, workplaces and public-health systems were not yet operating as though peak summer conditions had arrived.

A more extensive heatwave developed during the second half of June. Western Europe recorded an average temperature of 20.74°C for the month, 3.06°C above the 1991–2020 average and the region’s hottest June in the ERA5 climate dataset. Europe as a whole experienced its second-warmest June on record.

The geographical reach was exceptional. Germany reached 41.7°C at Coschen and reported all-time records at 252 weather stations. Denmark registered a national high of 37°C, while the Netherlands set a June record of 39.4°C. France recorded its hottest national-average day, and new monthly or all-time records were also reported in Austria, Hungary, Poland, Switzerland, Spain and the United Kingdom.

The sequence continued into July. Barcelona’s Fabra Observatory recorded 40.5°C on 8 July, the highest temperature in more than a century of observations there. At the same time, drought, dry vegetation and low humidity maintained severe wildfire danger in southern France and the Iberian Peninsula.

The immediate cause: persistent high pressure

The June heatwave was associated with a large, persistent area of high atmospheric pressure. Such systems can act as blocking patterns: they move slowly and interrupt the usual progression of Atlantic weather systems across Europe.

The position of the system produced sustained southerly airflow, carrying exceptionally warm air from North Africa into western and central Europe. It also suppressed clouds and rain, allowing strong sunshine to heat the land continuously.

High pressure intensifies heat through another process called subsidence, meaning the downward movement of air. As air descends, it is compressed by the greater atmospheric pressure below and becomes warmer. The combination of sinking air, weak cloud cover and prolonged sunlight raises temperatures near the surface.

Dry ground makes heat worse

By June, soils were already unusually dry across substantial parts of western and central Europe. River flows were also below average across much of France and central and eastern Europe.

Moist ground normally uses part of the sun’s energy to evaporate water. When the soil dries, less energy is consumed by evaporation, and more is converted directly into heat. The land then warms the air above it more efficiently.

This creates a reinforcing feedback: heat dries the ground, and dry ground enables still stronger heating. It also raises wildfire risk because vegetation loses moisture and becomes easier to burn.

What climate change changed

A blocking high is a weather event, not proof of climate change by itself. Comparable southerly circulation patterns occurred in the past. The critical difference is that they now operate over a warmer atmosphere, warmer seas and, in many locations, drier land.

World Weather Attribution compared the 2026 event with conditions in 1976 and 2003. Its analysis found that the large-scale circulation pattern was broadly similar to historical examples, but the temperatures produced by it were substantially higher because the climatic baseline had warmed.

A comparable June heatwave would have been approximately 3.5°C cooler during the day and 2.4°C cooler at night in the climate of 1976. Daytime heat of this severity was about ten times less likely in 2003 than today, while similarly extreme nighttime temperatures were more than 100 times less likely.

This is the most accurate way to describe the relationship: climate change did not need to create an entirely new weather pattern. It loaded an established pattern with additional heat.

What the rest of summer may bring

Seasonal forecasts cannot identify the date or location of the next heatwave. They estimate whether temperatures over a period of several months are more likely to fall above, near or below the historical range.

For July to September, the World Meteorological Organization’s multi-model outlook indicates an increased probability of above-normal temperatures across southern Europe, supported by moderate to strong agreement among forecasting systems. That does not mean continuous heat everywhere, but that the background risk remains elevated.

The central scientific conclusion is straightforward: the atmospheric ingredients that cause European heatwaves are familiar. The temperatures they now produce are not.

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