Historical heatwave in May: when will the temperature start to drop?

BarcelonaTemperatures have peaked this Thursday in many regions. We are experiencing the worst hours of this historic and premature heatwave, which today has already set new heat records for the month of May. In Vinebre (Ribera d'Ebre), a maximum of 38.5 ºC was recorded, equalling the May heat record, achieved in 2022 in Castellbisbal (Vallès Occidental) and Anglès (Selva). The Lleida station, with 86 years of data, has also broken its own May heat record, with 37.3ºC, and the centenary Ebre observatory has also broken its May record, with 37.3 ºC. The Raval neighborhood of Barcelona also reached its May heat record, with a maximum of 33.5 ºC, and some municipalities in Girona have broken their own records, such as Roses (Alt Empordà), with 34.4 ºC.

Furthermore, in Portbou (Alt Empordà), the record for the highest minimum temperature in May in Catalonia was reached, with 28 ºC, a circumstance known as a torrid night. An extraordinary event highly localized in this area due to the reheated tramuntana wind. For its part, the Fabra Observatory in Barcelona experienced its second warmest May night since records began in 1914, with a minimum of 23.4 ºC. We are under the effects of a powerful and long-lasting anticyclone that is causing what is known as the heat dome effect: the air does not circulate and we have strong solar radiation that heats the environment a lot, causing the heat to accumulate and become more intense day after day.

Tonight, tropical minimum temperatures will spread to many more places, especially along the coast, pre-coast, the south, and Ponent. It will be a night of poor sleep in some cases, and we will see if any other torrid minimum is reached. Friday, extreme heat will persist, and temperatures could brush 40 ºC in Ponent and the Ebro valley. However, temperatures will already recede slightly in the counties of Girona and Barcelona after today's torrid peak. A decrease that will become generalized over the weekend, although we will be coming from so high up that the atypical full summer atmosphere will be maintained. Afternoon showers will increase in the Pyrenees, and next week it could cool down more significantly.

Friday: very hot

Temperatures will remain very high and clearly above average for this time of year. Values between 8 and 12 degrees above the average in many cases. The night will be tropical in many parts of the coast, pre-coast, the south and Ponent, and maximums will again exceed 30 or 35 ºC in most regions. It will approach 39 or 40 ºC in Ponent and the southern interior, where we will see if new heat records are reached. On the coast, intense sultriness will be the protagonist. On the other hand, in the regions of Barcelona and Girona, the mercury will drop a little, although it will be very sultry there.

All this in a new anticyclonic day marked by scorching sun. In the afternoon, clouds will grow in the Pyrenees and Pre-Pyrenees, leaving some scattered showers. Nuances in a context of calm and a lot of heat for the dates.

Some changes over the weekend

Temperatures will drop on the weekend, but the atmosphere will remain fully summery, with values clearly above average. We are coming from very high up, and it will be very difficult to normalize the thermometers. Throughout next week, the maps indicate that we could have a cooling, although the end of this exceptional situation is not at all clear yet.

This weekend the center of the anticyclone will move to the Atlantic, which will favor more afternoon showers and thunderstorms in the Pyrenees and Pre-Pyrenees. With so much accumulated heat, we will see if any local downpour, hail, or hailstorm occurs. Throughout next week, showers could gain ground.