It has been, and still is, a summer with temperatures well above average across much of Europe, Italy included: we've felt it on our skin and are learning that we'll have to get used to it in the years to come. But what will happen when autumn arrives? Temperatures will probably remain higher than seasonal averages, and intense rainfall is likely to be more frequent, especially in the Mediterranean belt of Europe and, to the west, on the Iberian Peninsula — though without any certainty about amounts or frequency.

Yes, autumn will be quite warm too

This was the picture already painted before Ferragosto by Copernicus's update for the September–November 2026 quarter — a clear signal on heat, though less clear on rain and thunderstorms — and it is now confirmed by the findings of the LaMMA-CNR Consortium. Francesco Meneguzzo, a researcher at the national research consortium and its Commissioner, notes that "it is not possible to make a reliable forecast of a rainy autumn, nor to say that we will have three continuously warm months. Seasonal trends stem from large ocean-atmosphere system ensembles and differ from short-term forecasts."

What is certain is that autumn is starting from energy-laden conditions due to the state of the Mediterranean, which is itself emerging from a record summer: in July 2026, the average sea surface temperature reached around 27°C, the highest value since satellite measurements began in 1993. Seventy-nine per cent of the basin experienced at least one day of "strong" or higher marine heatwave, and off the coast of Tuscany the deviation from the 1991–2020 average reached nearly 4 degrees.

The most interesting data, however, concerns what cannot be seen from the surface: measurements by the LaMMA-CNR Consortium show that the excess heat reaches down to 70 metres depth in the Ligurian Sea. Translated into energy, this is an enormous quantity: "This excess heat represents an amount of energy estimated at 8.2 exajoules: as an order of magnitude, roughly 1.8 times the energy available for Italy's final consumption in 2024," explains Meneguzzo. "Energy that cannot technically be recovered and that was not accumulated in 2026 alone, but is a stock in excess relative to climatology." This is energy that, Meneguzzo explains, "lasts longer than thin surface warming, even if mixing and exchanges with the atmosphere can redistribute or attenuate it in the coming weeks."

Potentially very intense weather events

The question at this point is: what can this extra energy do in the short term? For example, a sea that is warmer than normal can transfer more heat and moisture to the atmosphere — an additional ingredient for intense weather events. Of course, it is only one ingredient, not a recipe already written: thunderstorms still require the right conditions, such as wind, humidity, instability, and orography. But the sea, under these conditions, can certainly amplify the scale of events.

On the soil front, the picture is patchy: drought alerts across parts of northern Italy, warning conditions in several areas of the Centre-North, and signs of normality or recovery in the Centre-South. And it should be remembered that arid ground is not automatically at greater risk of flooding — but here too it can heighten that risk, even though "rainfall intensity and duration, antecedent moisture, soil type and cover, slope, urbanisation, drainage networks and watercourse conditions are also important — these are local factors," Meneguzzo points out.

In mid-August, US research centres assigned more than 90 per cent probability to a very strong El Niño for autumn–winter. But its effect on Europe is indirect and inconsistent: it alone is not enough to explain the forecast warmth, nor to predict extreme rainfall in Italy. The experts' message is therefore one of caution, though not of alarm: a Mediterranean so laden with energy makes the starting conditions for autumn more unstable, even if the most reliable forecasts will only arrive as individual weeks draw closer.