Spain's Aemet warns of unusual late-May heatwave

Aemet warns of unusual pre-summer heat

Thermometers are set to record abnormally high values this week for the time of year. The State Meteorological Agency (Aemet) has warned that between May 29 and June 1, temperatures could reach their highest levels for these dates since at least 1950, with maximums 6 to 7 degrees above usual in much of the country. It is not summer, but the body will feel it as if it were: thermometers will climb to values typical of the peak heat period, which climatologically falls in the second half of July and first half of August.

The paradox is that this sudden arrival of heat comes after a spring that, during much of its development, recorded below-average temperatures. This contrast is precisely what amplifies the health impact: bodies receive the heat without prior acclimatization. "This is an episode of unusually high temperatures for this time of year and, although it is forecast to be short-lived (until the weekend), in some geographical areas it is expected that the threshold temperature defining a heatwave from a health risk perspective may be exceeded," confirms Cristina Linares, senior scientist at the Carlos III Health Institute.

Is it normal to record these temperatures in May?

No. Rubén del Campo, Aemet spokesperson, describes it as a "very warm episode, unusual for the time of year." Maximums will be between 5 and 10 ºC above normal in practically the entire Peninsula from Tuesday 27 until Sunday 1, and in some areas of the north, east, and south, more than 10 ºC above. José Miguel Viñas, meteorologist at Meteored, adds a nuance beyond the specific episode: "we are heading towards a new normality where these episodes of intense heat outside the summer period, both in spring and autumn, begin to become more likely."

The geographic extent is also notable. The episode affects practically the entire peninsula, with the Balearic Islands and Canary Islands joining in over the weekend, albeit to a lesser degree. From Thursday onwards, high temperatures will be accompanied by calima: an influx of Saharan dust that will cloud the skies on the Atlantic side and favor consecutive tropical nights, with minimums not dropping below 20 °C, in the central-southeastern peninsula and the Balearics.

The health impact of unacclimatized heat

As this is the first heatwave of the year, there may be a greater number of susceptible individuals whose pre-existing conditions worsen. Julio Díaz, research professor at the Carlos III Health Institute, warns that "there may be significant health impacts on particularly vulnerable groups such as elderly people, those with previous illnesses (cardiorespiratory, neurological, renal...), polypharmacy patients, dependent persons, low-income individuals, pregnant women, children, or people with intense outdoor work activity during midday hours."

Experts' recommendations do not differ much from those usual in summer, but with an added factor: lack of habit. Del Campo insists on protecting oneself from the heat, avoiding intense physical exercise during midday hours, and watching over elderly people and those with previous pathologies to prevent dehydration or heatstroke. Viñas reminds us that homes are still cool —an advantage that will be lost as the week pogre— and highlights a differential circumstance: "unlike summer, we are still in the school term, so students (especially the youngest) and teaching staff must be protected in the best possible way."

Controversy over records and 'cutting where convenient'

In terms of analysis, some observers question the time window chosen to proclaim records. It is argued that if the hottest day in May since 1950 is used as a reference, an earlier warmer year will always appear if the period is extended. The debate over whether late-May heat is exceptional or simply advanced summer intersects with another underlying issue: comparison with historical records from the early 20th century, when maximums exceeding 40 degrees were already documented in Seville in May, although with a much smaller urban heat island effect than currently.

What all sources admit is the anomaly of the context. This spring has alternated episodes of below-average temperatures with a ridge of warm air installed over the vertical axis of the peninsula that now sends thermometers soaring. The persistence of anomalous weather patterns is, in itself, the data meteorologists point to as most significant.

What can be expected in the coming days?

According to Aemet, the episode will be short-lived: until the weekend. Temperatures will begin to drop from Sunday onwards, although the calima will persist for several days. The combination of intense heat, tropical nights, and suspended dust will keep health risks high for vulnerable groups even after maximums subside.

The lingering question is not whether it will be hot —that is guaranteed— but whether this type of early episode will become the norm every May. Data from recent years suggest yes, but the historical series is short enough that no one dares to close the forecast.