Historic heat: Five surprising facts from June

BarcelonaEveryone imagined it would be, but now the data confirms it: Catalonia has experienced the warmest June in its history since records began, according to the preliminary monthly report from the Catalan Meteorological Service (SMC). The monthly temperature across the country was 4°C above the average for the reference period (1991-2020), an extraordinary and unprecedented anomaly.

In fact, June 2025 has surpassed the 2003 record, which held the heat record until now, followed closely by June 2022. The key to understanding these figures is the persistent and sustained heat that has dominated throughout the month due to the constant arrival of temperatures, with values above average day after day. In fact, there have been days when the temperature anomaly with respect to the average has exceeded 5°C or 6°C. And the icing on the cake has been the heat wave of the last few days, which has brought the most extreme temperatures so far this year and which will continue through the first two days of July.

All of this has led to several heat records. As many as nine SMC stations with more than twenty years of data have equaled or broken their own records. Particularly noteworthy are those achieved by the Fabra Observatory in Barcelona, ​​​​which, with 112 years of data, recorded its warmest June ever, with an average temperature of 26°C, four-tenths of a percentage point above the 2003 record and 4.7°C above average. Furthermore, Monday—the last day of the month—reached the highest temperature ever recorded in June at this point, at 37.9°C. Finally, June was the eighth warmest month in the entire centenary series recorded at this observatory, where, in addition, four of the five warmest days in June were recorded during the last week.

Many municipalities have also experienced days of historic heat, but in most cases the maximum temperature records recorded during the extraordinary heat wave at the end of June 2019 have not been broken. A small nuance in a context of permanent stifling atmosphere, with maximums that in these last few days of the Ebro) and have reached or exceeded 40 °C in many points of Ponent, the Ebro, Priorat and Alt Empordà.

Heat records at night and at sea

The night has also been very hot, with tropical lows in many regions, and even torrid temperatures (over 25°C) in some coastal areas. Eight SMC stations with more than twenty years of data have recorded their warmest June night since their records began.

The case of the city of Barcelona stands out, having now accumulated twelve consecutive torrid nights, again a record figure in the country that even surpasses the records of 2003. The two main factors explaining these data are the urban heat island effect and seawater, which is in the seawater. Quite widespread nights of poor sleep that almost left what is known as red night –minimums above 30°C– in Portbou (Alt Empordà).

But the heat wave isn't limited to land. The water in the Mediterranean Sea is excessively warm, with temperatures more typical of the dog days of summer, reaching 5°C above average in some cases. According to data from the Catalan Institute for Research on Marine Governance (ICTAMAR), the average temperature of all Mediterranean waters reached 26.38°C on June 27, the highest value recorded for this month.

In Spain, the data from Estartit (Baix Empordà) provided by observer Josep Pascual stand out, the oldest and most reliable series in the entire Mediterranean. At that coastal point, the water was at 24.54°C on Monday, the highest temperature recorded in this area in June in half a century of data. Also noteworthy is the Sa Dragonera buoy (Mallorca), which for the first time exceeded 30°C in June, reaching the scandalous figure of 30.55°C.