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, equaling the May heat record, achieved in 2022 in Castellbisbal (Vallès Occidental) and Anglès (Selva). 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 highest minimum temperature record for a May in Catalonia was reached, with 28 ºC, a phenomenon known as a tropical night. An extraordinary event very localized in this area due to the re-heated tramuntana wind. For its part, the Fabra Observatory in Barcelona has experienced its second warmest May night since records began to be taken, 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 considerably, causing the heat to accumulate and become more intense day after day.

Tonight, tropical lows will extend to many more places, especially along the coast, the 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 low is reached. On Friday, extreme heat will be maintained, and temperatures could reach 40 ºC in Ponent and the Ebro valley. However, temperatures will already recede slightly in the regions of Girona and Barcelona after today's torrid peak. A decrease that will become widespread on the weekend, although we will be coming from so high up that the atypical mid-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 average in many cases. The night will be tropical in many parts of the coast, pre-coast, south and Ponent, and maximums will once again exceed 30 or 35 ºC in most regions. We 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 mugginess will be the protagonist. On the other hand, in the regions of Barcelona and Girona the mercury will recede a little, although it will be very muggy there.

All this in a new anticyclonic day marked by sunshine. In the afternoon, clouds will grow in the Pyrenees and Pre-Pyrenees, leaving some scattered showers. Nuances in a context of calm and very hot weather for the dates.

Some changes over the weekend

Temperatures will drop at 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 thermometers. Throughout next week, the maps indicate that we could have a cooling down, although the end of this exceptional situation is not yet at all clear.

This weekend, the center of the anticyclone will move to the Atlantic, which will favor the appearance of 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, the showers could gain ground.