Ibiza and Formentera are expected to experience a warmer-than-usual autumn, while rainfall is forecast to remain broadly within normal seasonal levels, according to the latest guidance from the State Meteorological Agency, AEMET.

The forecast comes almost one year after exceptionally intense rainfall caused flooding and significant damage across Ibiza in late September and October 2025.

Meteorologists are stressing that an average rainfall forecast does not mean the islands are protected from torrential downpours.

Warmer Conditions Expected

AEMET's local forecast for the autumn period indicates that average temperatures are likely to remain above the normal values for Ibiza and Formentera.

Using the 1991-2020 reference period, the expected average temperature is around 15°C for Ibiza and 16°C for Formentera across the October-December period cited in the local forecast. Temperatures are expected to decline progressively through the season.

In October, the corresponding averages are around 19°C in Ibiza and 20°C in Formentera, falling to approximately 15°C and 16°C in November and 12°C and 13°C in December.

Rainfall Expected Around Seasonal Norms

For the October-December period, AEMET's local forecast indicates rainfall around the usual seasonal amount.

The average rainfall cited is approximately 237 litres per square metre in Ibiza and 139 litres per square metre in Formentera.

That figure refers to accumulated precipitation over the season and does not mean rain will be evenly distributed between days or months.

Normal Rainfall Does Not Mean No Flood Risk

This is one of the most important points in the forecast.

AEMET's seasonal models provide information about the overall amount of precipitation expected during a period. They cannot determine several months in advance exactly when individual storms will occur or how intensely rainfall will be concentrated.

A season with an overall normal rainfall total can therefore still contain one or two extremely intense episodes.

AEMET's own explanation of seasonal forecasting emphasises that these products are probabilistic rather than day-to-day weather predictions.

Torrential Rain Is Still Possible

María José Guerrero Trujillo, AEMET's territorial delegate in the Balearic Islands, has stressed that torrential rainfall remains possible during the autumn.

The meteorological conditions that can produce these events include high sea-surface temperatures combined with atmospheric disturbances and favourable wind patterns.

According to Guerrero Trujillo, those disturbances can include DANAs, fronts, upper-level troughs and wind convergences. A DANA is therefore not the only type of weather system capable of producing torrential rainfall in the Mediterranean during autumn.

The Mediterranean Sea Plays a Major Role

Warm Mediterranean waters can provide additional energy and moisture to developing storms.

AEMET explains that when an atmospheric disturbance interacts with a warm sea, the resulting instability can produce very intense rainfall.

This also explains why a similar atmospheric configuration can produce very different rainfall intensities depending on the season and the state of the sea.

What Can Produce a Torrential Event?

For a DANA to generate exceptionally heavy rainfall over Ibiza and Formentera, several conditions need to coincide.

A pocket of cold air at altitude can combine with converging winds near the surface, forcing warm and humid air upwards. If the atmosphere is sufficiently unstable, this can produce clouds with significant vertical development and intense thunderstorms.

Such storms can also bring very strong wind gusts, hail, waterspouts and, in some circumstances, tornadoes.

Last Year's Rainfall Was Exceptional

The concern about another major event comes from what happened in autumn 2025.

Ibiza experienced two episodes of extreme rainfall within less than two weeks, on September 30 and October 12.

The September episode produced exceptionally high rainfall totals in parts of the island, while the October event was associated with the DANA Alice. The incidents caused flooding and damage to roads, buildings and other infrastructure.

AEMET's national climate reporting confirms that the end of September 2025 brought torrential rainfall to parts of the Balearic Islands.

When Can Dangerous Weather Be Identified?

Seasonal forecasting cannot identify a specific storm months in advance.

According to Guerrero Trujillo, a potentially dangerous weather situation can sometimes begin to appear in forecast models around 10 to 15 days beforehand, with confidence increasing significantly as the event approaches.

Two or three days before a potential event, additional forecasting models and new observations can provide a clearer picture.

This is why residents should not interpret the seasonal forecast as an indication that a particular type of storm will or will not occur.

AEMET's Current Seasonal Product

AEMET's publicly available seasonal forecast currently covers September, October and November 2026.

For that period, the agency places temperatures in the upper tercile with high probability across Spain, with the warm signal particularly strong in the Balearic Islands. It also shows a greater probability of precipitation being in the upper tercile in the Balearics.

This illustrates why seasonal forecasts need to be read in terms of probability and the exact period being measured.

Autumn Will Gradually Become Cooler

Although the overall seasonal temperature outlook is warmer than normal, temperatures will still decline naturally as autumn progresses.

The local forecast gives average temperatures of approximately 19°C in Ibiza and 20°C in Formentera in October, falling to around 12°C and 13°C respectively by December.

The warmer-than-normal forecast therefore does not mean summer conditions will continue throughout the season.

Rainfall Pattern Expected to Change

The local forecast also anticipates a change in the character of rainfall as autumn progresses.

The first part of the season can bring isolated heavy showers and thunderstorms, including events accompanied by hail and strong winds.

From November onwards, rainfall is generally expected to become more moderate and widespread, although individual heavy episodes can still occur.

Ibiza's Weather Can Change Quickly

The forecast is particularly relevant to Ibiza because the island can move rapidly between prolonged dry periods and short episodes of intense rainfall.

A relatively dry month does not necessarily mean that flood risk is absent. Conversely, a season with average accumulated rainfall can still contain an isolated extreme event.

That distinction is central to understanding AEMET's warning that normal seasonal rainfall totals should not be interpreted as a guarantee against torrential rain.

Residents Should Continue to Follow Short-Range Warnings

AEMET's seasonal forecast is useful for understanding broad climate tendencies, but residents and visitors should rely on short-range forecasts and official warnings when severe weather is approaching.

Those updates provide information about specific rainfall, wind and storm risks that seasonal forecasts cannot provide months ahead.

During potentially severe episodes, AEMET and the relevant emergency authorities issue more detailed warnings as the situation develops.

A Warmer Autumn With Continued Weather Uncertainty

The broad message for Ibiza and Formentera is therefore one of higher-than-normal temperatures, but continued uncertainty over when and how rainfall will occur.

The overall amount of rain may remain close to seasonal norms over the autumn period cited by the local forecast, but that does not eliminate the possibility of intense storms.

After the exceptional events of 2025, AEMET's message is that the conditions that produce torrential Mediterranean rainfall remain possible, even during an autumn that is not unusually wet overall.

What to Expect

For Ibiza, the coming autumn is currently expected to bring:

Temperatures: Above normal
October: Around 19°C average in Ibiza and 20°C in Formentera
November: Around 15°C and 16°C respectively
December: Around 12°C and 13°C respectively
Rainfall: Around seasonal norms for the October-December period cited locally
Heavy rain: Still possible in short, intense episodes
Storm hazards: Heavy showers, thunderstorms, hail, strong winds, waterspouts and, in some circumstances, tornadoes

The forecast is not a prediction that Ibiza will avoid another major storm. Instead, it indicates that an autumn with average accumulated rainfall can still include isolated episodes of very intense weather.