From the summer heat to the rains throughout the Catalan Countries: what awaits us this autumn?

BarcelonaThe astronomical autumn is here, putting a definitive end to the hottest summer in history since temperature records began. The new season officially starts this Wednesday at 02:05, which is when the equinox takes place, and will last until December 21st, when winter begins.

Autumn is the rainiest season of the year in a large part of the country, especially on the coast, the pre-coastal area, and the northeast quadrant. Therefore, the water that falls during this time is key to determining whether a year has been dry or wet. Furthermore, it usually concentrates the most significant downpours and storms. Rains that are becoming more torrential every year due to the effects of the climate crisis, especially fueled by the increasingly high sea temperature. Therefore, will it rain a lot in these coming months? Will it be a warm autumn again?

Below, we break down what the seasonal forecasts say.

Risk of heavy rain

Regarding precipitation, long-term maps indicate a clear trend that October may be “extremely rainy” on the coast and nearby areas, as explained in statements to ARA by Sant Segalà, head of the Forecasting Area of the Meteorological Service of Catalonia (Meteocat). A forecast that extends broadly to the entire western Mediterranean, fully encompassing Catalonia, the northern half of the Valencian Community, the Balearic Islands, and Northern Catalonia.

“This makes us think that we could have large-scale disturbances or easterly storms, rather than isolated episodes,” adds Segalà, who also reminds us that such long-term models show trends and must be taken with a grain of salt, because they have less reliability.

It must be taken into account that the sea is exceptionally warm this year, after experiencing an exceptionally scorching summer. A factor that will be key, as it can cause the rains to be much more intense and torrential than normal. “If a DANA, an easterly storm, or a large Mediterranean low-pressure system were to arrive, we could have much more extensive and intense precipitation, which is what causes the most concern,” warns Segalà.

“We have the sea-atmosphere system doped by heat, which, in an extraordinary and persistent way for months, has been charging it. With all this energy available, in the event that some large-scale disturbance arrives, we would no longer be talking about local downpours like the ones we have had in recent weeks, but rather they would be more extensive,” adds Segalà. And he warns: “Statistically, episodes of extraordinary rain like the one experienced two years ago in Valencia can unfortunately happen again.”

Regarding November, the maps indicate that it would be slightly rainy, and in December little rain would fall, coinciding with the beginning of winter. Therefore, the autumn as a whole may be rainy, which would favor the growth of mushrooms, a highly valued and awaited product every year. In any case, it will be necessary to follow the weather forecast very carefully week by week to go about confirming these scenarios.

New warm autumn

Regarding temperatures, all maps indicate that it will be hot again, with values clearly higher than usual for this time of year. In fact, the first days of the new season will continue to be marked by an atypically summer-like environment, and September may close with an anomaly of more than 2 ºC in relation to the average, an extraordinary figure.

“The models maintain that we will return to having a warm autumn throughout all the months, until December,” assures Segalà. In this sense, the maps indicate that October and November could record an average temperature of more than 1 ºC above the usual on the coast, and half a degree in the rest of the regions. This anomaly would be between 1 and 1.5 ºC in general looking towards December.

Therefore, everything indicates that, one more year, we will have to eat the 'panellets' and chestnuts in short sleeves. It must be said that, despite these forecasts, during the second part of autumn, the first inflows of cold air and light dustings or snowfalls usually arrive in the high altitudes of the Pyrenees. Situations, however, that are increasingly sporadic in the context of constant warming.

Heat waves aggravated by emissions

Greenhouse gas emissions produced since the signing of the 2015 Paris Agreement have an impact on all of this, as they have intensified extreme heat waves in Europe. This is the conclusion of a study by Stanford University in California (United States), published in the journal Geophysical Research Letters, coinciding with the official end of the boreal summer. The work concludes that there is a probability of over 99% that the accumulated emissions since 2015 made the June 2025 heat wave more intense. Researchers estimate that they raised average daily temperatures in some European areas by approximately a third of a degree.

The study also points out that this effect is not limited to the summer of 2025: emissions after the Paris Agreement would have contributed to intensifying the hottest weeks recorded in Europe each year since 2021. To reach these conclusions, climate models, real meteorological data, and an artificial intelligence (AI) system capable of comparing current temperatures with those that would have occurred with 2015 emission levels have been combined.

The authors remark that an increase of a third of a degree may seem small, but in extreme episodes, it can have significant consequences on mortality, electricity demand, agriculture, and productivity. The study further warns that even if global emissions begin to be reduced successfully, the accumulated warming will cause extreme heat waves to continue intensifying in the coming years.