Europe is enduring an intense and early heatwave this week, with temperatures soaring to levels more typical of July than mid-May. Across Portugal, Spain, and France, daytime highs have reached 38°C, while Germany and the United Kingdom have seen thermometers climb above 30°C. The cause, according to Météo-France and Severe Weather Europe, is a powerful and highly anomalous heat dome that has parked over Western and Central Europe.
A heat dome forms when a high-pressure system develops in the upper atmosphere, causing the air below to sink and compress. This compression raises temperatures in the lower atmosphere, and because hot air expands, it creates a bulging dome that traps heat. Normally, winds can move high-pressure systems, but heat domes extend so far into the atmosphere that they become nearly stationary. The result is a prolonged period of extreme heat that dries out the ground and increases the risk of wildfires.
While the term “heat dome” has been around for decades, it only entered popular usage in the 2010s. It has since suffered from what some meteorologists call the tabloidisation of weather phenomena, alongside terms like “polar vortex” and “snow bomb.” Many people now mistakenly use it as a synonym for a heatwave. In reality, a heat dome is a specific atmospheric configuration that can cause a heatwave, but the two are not the same. The UK Met Office defines a heatwave as an extended period of hot weather relative to the expected conditions for a given area and time of year, often accompanied by high humidity.
Why This May Heat Is Unprecedented
Severe Weather Europe reports that temperatures are running 12–16°C above long-term climatological norms. The forecaster warns that “air mass will be even hotter in the coming days for many countries, as the Heat Dome aloft intensifies further. Because this pattern restricts vertical mixing and cloud cover, maximum and minimum temperatures alike will challenge historical monthly records across hundreds of stations in Western Europe.” France has placed large parts of the country under a moderate high-temperature warning, and similar alerts are in effect in Spain and Portugal.
This early heat is not an isolated event. According to the EU’s Copernicus Climate Change Service (C3S), 2025 was the third-hottest year on record globally and in Europe. The three hottest years on record globally are, in order, 2024, 2023, and 2025. Last year, temperatures exceeded 40°C in dozens of nations, pushing countries into drought, igniting wildfires, and killing thousands. Researchers at Imperial College London and the London School of Hygiene & Tropical Medicine examined 854 European cities and found that climate change was responsible for 68% of the estimated 24,400 heat-related deaths last summer, having raised temperatures by up to 3.6°C.
The hardest-hit region during a single heatwave last year was the Balkans. From 21 to 27 July, an estimated 950 heat deaths occurred in Romania, Bulgaria, Greece, and Cyprus, where temperatures reached up to 6°C above average. That equates to roughly 11 daily deaths per million people.
Ioanna Vergini, a forecaster with WFY24, told Euronews Earth that the European summer is not just getting hotter—it is getting longer at both ends. “What we used to call a July phenomenon is now arriving in mid-May,” she said. “Climate attribution studies estimate that June heatwaves in Europe are around 10 times more likely today than they were in pre-industrial conditions, and the same trajectory is becoming visible for May.”
A 2025 study published in Proceedings of the National Academy of Sciences found that atmospheric patterns that lock in extreme weather—such as heat domes and flooding—have nearly tripled since the 1950s due to human-driven climate change. This trend is consistent with the broader pattern of a warming planet, where extreme events become more frequent and intense.
As Europe swelters under this May heat dome, the question of preparedness looms large. Many cities and countries have heat action plans, but the early arrival of such extreme temperatures tests their effectiveness. The Spring Heat Surge Tests Europe's Readiness as authorities scramble to protect vulnerable populations, from the elderly to outdoor workers. Meanwhile, the continent’s water reserves are under additional strain, with Europe's Largest Underground Water Reserve Under Threat from Pollution already facing challenges from over-extraction and contamination.
For now, the heat dome is expected to persist for several more days, with little relief in sight. Forecasters advise residents and visitors in affected areas to stay hydrated, avoid strenuous outdoor activity during peak heat, and check on elderly neighbours. The episode serves as a stark reminder that climate change is not a distant threat but a present reality reshaping the European seasons.
