May began unseasonably cool across Spain, with temperatures below normal in most regions. But since 19 May, a persistent high-pressure system stretching from North Africa to the British Isles has transformed the landscape, bringing heat more typical of July or August.
Meteorologists call this phenomenon an anticyclonic ridge, or more colloquially, a heat dome. The mechanism is straightforward: the anticyclone acts as a lid, preventing air renewal and compressing the air, which heats it further. The result is stifling conditions that have pushed temperatures up to 15°C above the seasonal average in some areas.
Spain's state weather agency, AEMET, has documented remarkable anomalies. At Santander airport, where records date back to 1954, temperatures above 30°C before June had only been recorded on two days. This year, there have already been six. At Badajoz Airport, with 71 years of data, temperatures above 38°C were recorded in May for the first time.
Regional Impact and Forecast
The heat is not confined to Spain's south-west. The Cantabrian north, the Ebro valley, and much of western Europe are experiencing similar extremes. In Spain, the hardest-hit provinces include Badajoz, Seville, Córdoba, Jaén, Toledo, and Zaragoza, where highs have ranged between 37°C and 39°C for days. In the south, temperatures could approach 40°C later this week.
The Ebro valley, historically one of the peninsula's hottest areas, is living up to its reputation. But the most striking aspect is the heat in the north. Bilbao is nearing its highest May temperatures on record, while Cantabria, Asturias, and inland Galicia are also seeing levels far from normal.
Forecasts suggest a slight easing in the far north-west by the weekend, but an intensification further east. On Friday, temperatures could reach 36°C in Madrid, 38°C in Seville, and up to 39°C in Lleida and Zaragoza. Any relief is unlikely before the weekend, meaning Spain will see out May and welcome June under this heat dome.
Experts highlight the phenomenon of tropical nights, when the thermometer does not drop below 20°C. In provinces such as Cádiz, Seville, and Barcelona, minimum temperatures will hover around or exceed that threshold for several consecutive nights. This is particularly concerning because when the body cannot recover during sleep, heat stress accumulates day after day. Doctors warn that these nights without respite, more than daytime peaks, have the greatest impact on public health, especially among older people and those with chronic illnesses.
Europe-Wide Records and Fatalities
The episode extends beyond Spain. In the United Kingdom, where such temperatures are far more exceptional, Kew Gardens in London reached 34.8°C, beating the previous May record of 32.8°C set in 1922. The following day, the record was broken again with 35.1°C, and the country endured several tropical nights, virtually unprecedented for May.
France has seen the harshest side of the episode. Temperatures near London reached 35°C, and some areas of France and Spain could climb to 39°C. French authorities placed several western departments on orange alert for the first time in May. Two people died while doing sport, one in Paris and another in Lyon. Italy is also registering record May temperatures.
The week of 25 to 31 May 2026 could go down in Europe's climate history for these extreme readings, which far exceed typical summer values. Meteorologists warn that temperatures are soaring between 12°C and 16°C above long-term climatological norms, as greenhouse gases continue to heat the planet.
Climate attribution studies estimate that June heatwaves in Europe are now around ten times more likely than under pre-industrial conditions, and the same trend is emerging in May. What used to be brief surges of spring warmth is gradually becoming the new baseline. As Germany risks missing its 2030 climate goal while Spain surpasses its target, the contrast in national efforts underscores the urgency of adaptation.
The question many are asking is whether episodes like this were normal in the past. The answer is nuanced: spring heatwaves have always existed, but their intensity, extent, and duration are now different. This heat dome is not a blip but a sign of the new norm, driven by a warming planet.
