‘Heat dome’ turns May into August in Spain: highs near 40C
May began on a cool note. During its first few weeks, temperatures in Spain were below normal across almost the entire country. Nothing hinted at what was to come. Since 19 May, however, thermometers have...
May began on a cool note. During its first few weeks, temperatures in Spain were below normal across almost the entire country. Nothing hinted at what was to come. Since 19 May, however, thermometers have been climbing steadily, reaching values that would normally belong in the height of summer.
The culprit is a high-pressure system stretching from North Africa to the British Isles, which meteorologists call an anticyclonic ridge, or, in more popular terms, a heat dome.
The mechanism is simple: this anticyclone acts like a lid that prevents the air from being renewed, forces it to sink and, as it is compressed, heats it even further. The result is stifling conditions that drag on for days and which, in some places, mean an anomaly of up to 15°C above the usual values for this time of year. In other words: the kind of heat that would normally arrive in July or August has turned up two months early.
AEMET has noted that at Santander airport, where records go back to 1954, temperatures above 30°C before June had only been recorded on two days. This year there have already been six. At the Badajoz Airport weather station, with 71 years of data, temperatures above 38°C have been recorded in May for the first time in the entire series.
The anomaly does not respect geography: the episode is hitting the south-west of the peninsula, the Cantabrian north, the Ebro valley and much of western Europe alike.
Where the heat is fiercest and what to expect in the coming days
Within Spain, the heat is unevenly distributed but with few places spared. The south-western quadrant has been posting highs of between 37 and 39°C for days, and in some parts of the south temperatures could brush 40°C in the second half of the week. Badajoz, Seville, Cordoba, Jaen, Toledo and Zaragoza are among the hardest-hit provinces.
The Ebro valley, which has a long history as one of the peninsula’s great furnaces, is living up to its reputation once again. But the most striking aspect of this episode is what is happening in the north. Bilbao is approaching the highest temperatures ever recorded there in May. Cantabria, Asturias and inland Galicia are also seeing levels far from normal.
Forecasts for the rest of the week point to a slight easing in the far north-west, 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 let-up, if it comes, will not be before the weekend. That is how Spain will see out May and welcome June.
One factor experts repeatedly highlight is tropical nights, when the thermometer does not drop below 20°C. In provinces such as Cadiz, Seville or Barcelona, minimum temperatures will hover around or exceed that threshold for several nights in a row.
The problem is not just the muggy heat: when the body does not manage to recover during sleep, heat stress builds up day after day. Doctors warn that it is precisely those nights without respite, more than daytime peaks, that have the greatest impact on public health, especially among older people and those with chronic illnesses.
Europe on alert: records and first victims
The episode is not confined by borders. In the United Kingdom, where such temperatures are far more exceptional than in southern Europe, they reached 34.8°C in Kew Gardens in London, beating the previous May record of 32.8°C set in 1922 and equalled in 1944.
The following day the record was broken again, with 35.1°C, and the country has endured several days with tropical nights, something virtually unprecedented for this month.
France has seen the harshest side of the episode. The mercury reached 35°C near London and could climb to 39°C in some areas of France and Spain. The French authorities placed several departments in the west of the country on orange alert, something never before seen in May. In France, two people have died while doing sport, one on Sunday in Paris and another on Monday 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 the extreme readings recorded, which go far beyond the high values typical of summer. 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.
The question many people are asking is whether episodes like this used to be normal. The answer is nuanced. Spring heatwaves have always existed, but their intensity, extent and duration are now different.
Climate attribution studies estimate that June heatwaves in Europe are now around ten times more likely than they were under pre-industrial conditions, and the same trend is beginning to emerge in May. What used to be brief surges of spring warmth is gradually turning into the new starting point.
