Europe’s hottest – A three-day heatwave across western and central Europe reached record levels of heat and humidity on 24 June, with temperatures far hotter than typical conditions decades ago. A new World Weather Attribution study says global warming is to blame, and warns hum
On 24 June, extreme heat settled over much of Europe—and this time it didn’t just break the thermometer. It moved into the part of the climate story that can feel hardest to quantify: the air itself.
A study by the World Weather Attribution network of scientists says this week’s heatwave is the hottest three-day period ever recorded in Europe, and also the most humid. The researchers warn it is likely to cause thousands of deaths.
The timing mattered. Over the past three days, a low-pressure “heat dome” trapped hot air coming from the south. The weather pattern is not unusual, the study found. What’s different is the scale. The temperatures seen during this event would have been about 3.5°C cooler in a typical June heatwave 50 years ago. Over the past three days, the likelihood of such temperatures happening is described as less than a one-in-10,000-year occurrence.
Daytime heat pushed beyond 44°C (111°F) in at least one French town. At night, the danger didn’t ease. Nighttime temperatures stayed above 30°C (86°F) in parts of Spain.
At a media briefing on 25 June. Theodore Keeping at Imperial College London laid out what the numbers mean in practice: “This event would not have been possible in June without climate change. ” he said. He added that “the three-day nighttime temperatures would not have been possible at any time of year without climate change.”.
The humidity is what may make this particular heatwave especially merciless. The study says humidity has been unprecedented, reaching more than 50 per cent in many British cities. Dew-point temperatures have been in the low 20s. compared with single digits during the July 2022 heatwave that set the UK’s temperature record.
That combination—heat plus moisture—matters because sweating, the body’s main cooling system, depends on evaporation. With humid air, evaporation slows, and the body can struggle to cool itself.
To capture that interaction, the researchers looked at wet-bulb globe temperature, a measure that accounts for air temperature as well as humidity, heat radiation and air movement. The study found it has broken or is expected to break records in almost half of European cities.
As the study rejects the idea that a newly forming climate pattern in the Pacific is driving this event, the human fallout becomes the focus. Although a potential “super El Niño” is forming in the Pacific Ocean, the study says it did not play a role in the heatwave.
Keeping also warned that the health impacts are likely to be extremely high across large parts of northern and central Europe. It is still too soon to calculate excess mortality for this episode. but the researchers point to a previous benchmark: a smaller heatwave in June and July of 2025 killed 2300 people in London and 11 other European cities.
Humidity also changes who is at risk. The study notes older people or those with a chronic illness are in particular danger, but it is not only about age or diagnoses. It also flags migrants and people experiencing homelessness as vulnerable.
Friederike Otto. also at Imperial College London. described the unequal toll in stark terms: “What we see very clearly… is how unequal the effects of this heatwave are and how that really demonstrates the inequality that widens due to climate change. ” she said. “Because it’s of course people who are particularly vulnerable who are most likely to lose their lives.”.
The researchers’ message then turns to prevention—both in the climate sense and in the practical, local sense. Heatwaves will become even more intense and frequent unless fossil fuel emissions are cut rapidly. And Europe, described as the fastest warming continent, is not prepared for the conditions it is already facing.
The problem isn’t just weather. It’s built for a different era. The study points to an ageing, urban population living in cities designed for cooler conditions. In the UK, only 5 per cent of buildings have air conditioning.
Beyond air conditioning. the researchers say Europe should invest in passive cooling measures such as building insulation. ventilation. green roofs and walls. and trees along streets. They also want heat response plans expanded to include groups that are often overlooked—people with mental health conditions and those who are pregnant.
Carolina Pereira Marghidan at the Red Cross Red Crescent Climate Centre said: “Europe has heat action plans, but research has also shown that sometimes they do not cover all the groups that may be vulnerable.”
With daytime temperatures already above 44°C in parts of France and nights holding steady above 30°C in Spain. the heatwave is no longer a distant forecast. It is a live test of how quickly societies can respond—one measured not only in degrees. but in the humidity that makes cooling harder and risk harder to ignore.
Europe heatwave humidity wet-bulb globe temperature World Weather Attribution climate change Imperial College London Theodore Keeping Friederike Otto Red Cross Red Crescent Climate Centre El Niño heat action plans air conditioning