May began on a cool note. During its first few weeks, temperatures in Spain were below normal across almost the whole country. Nothing hinted at what was to come next. Since 19 May, however, thermometers have risen steadily, reaching values that would normally correspond to 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 renewal of air, forces it to descend and, as it is compressed, heats it even further. The result is a stifling atmosphere that does not let up for days and that, in some places, represents an anomaly of up to 15 °C above the usual values for this time of year. In other words, the heat that would normally be expected in July or August has arrived two months early.
AEMET has recalled that at Santander Airport, with data going back to 1954, temperatures above 30 °C had only been recorded before June on two days. This year there have already been six. At the Badajoz Airport observatory, with 71 years of records, temperatures of more than 38 °C have been recorded in May for the first time in the entire historical series.
