Spain swelters under record-breaking May heat dome as meteorologists warn summer is 'gaining ground on spring'
An extraordinary late-May heatwave has shattered temperature records across Spain, with the mercury hitting 37.5°C and nights offering no relief as a persistent anticyclonic 'heat dome' traps scorching air over the Iberian Peninsula and western Europe.
Spain is enduring an episode of extreme heat that meteorologists have described as 'extraordinary' and 'totally unusual' for late May, with temperatures more typical of July or August. The State Meteorological Agency (AEMET) has confirmed that numerous records have been broken, including 37.5°C in Tortosa/Roquetes, which smashed the previous May record by nearly 1.5°C, and 36.3°C in Zamora for the second consecutive day. The heat is not confined to daylight hours; ten municipalities are forecast to experience minimum temperatures above 25°C in the early hours of Saturday, with Alcázar de San Juan, Linares, and Zaragoza expected to remain at 27°C at 1 a.m.
What is causing the extreme heat?
Meteorologists attribute the scorching conditions to a large, stationary anticyclone parked over Europe. This high-pressure system acts as a 'lid', compressing and heating the air as it descends, while blocking cooler, unstable weather systems. Roberto Brasero explained on Antena 3 that the anticyclone is 'very persistent and very extensive', reaching up into the middle and upper layers of the atmosphere and forming an 'invisible dome where the heat gets trapped'. Martín Barreiro described a 'omega configuration' over the continent, with the anticyclone stuck between two low-pressure zones, remaining 'stationary over Europe like the lid on a pot'.
This anticyclone that we have now is very persistent and also very extensive, not only because it reaches France or the United Kingdom, but because it also extends upwards.
While the term 'heat dome' has become popular, AEMET notes that the scientifically precise term is a blocking anticyclonic ridge. The agency has also pushed back against online misinformation, including false claims that the heat is cyclical or caused by chemical trails from aircraft.
Records tumble and seas overheat
The heatwave has produced striking anomalies. Barcelona Fabra recorded a minimum temperature above 23°C, while the Mediterranean Sea around the Balearic Islands is 3.5 to 4°C above normal. The Cantabrian Sea in the Bay of Biscay is even more extreme, at 5 to 6°C above average. AEMET spokesperson Rubén del Campo warned that such episodes are becoming more frequent, stating that 'summer is gaining ground on spring' and that Europe, especially the south, is warming rapidly.
The most likely scenario is that we will have episodes of very high temperatures more frequently.
A weekend of scorching days and explosive storms
The forecast for Saturday offers little respite. Daytime maximums will again exceed 34-36°C across most inland areas of the southern half of the peninsula and the northeastern depressions, potentially reaching 40°C in some spots. The heat will be accompanied by a contrasting risk of dry storms with very strong wind gusts in central areas, and locally heavy showers with hail in the Pyrenees and the Iberian range.
- Tortosa/Roquetes records 37.5°C, breaking its May record by nearly 1.5°C. Zamora hits 36.3°C for a second day.
- AEMET warns of extraordinary heat persistence with no return to normal in sight. Barcelona Fabra records a minimum above 23°C.
- Ten localities forecast to remain at 25-27°C at 1 a.m., including 27°C in Alcázar de San Juan, Linares, and Zaragoza.
- Daytime highs of 34-36°C expected across southern and northeastern inland areas, with dry storms and hail risk in the Pyrenees.
- Possible general relief from the heatwave across the peninsula, though temperatures will remain above normal.
Health impacts and the struggle to cool down
The persistent heat, especially the lack of nighttime cooling, places significant strain on the human body. The Ministry of Health has issued guidance on recognizing heat-related symptoms such as headaches, nausea, dizziness, and a rapid, weak pulse. Scientific research indicates that prolonged exposure to high temperatures forces the brain to divert resources to thermal regulation, reducing performance in areas linked to attention, emotion, and decision-making. This can lead to decreased academic and workplace productivity.
The heat dome is one of the reasons we are experiencing an episode of extreme heat that is totally unusual for this time of year.
AEMET currently sees no return to normal temperatures in the immediate future, with the warm episode likely to persist for several more days. While some relief is expected in the north over the weekend and more generally by Tuesday, temperatures next week are still forecast to remain above the seasonal average.
