The ECMWF’s seasonal data for September point to a warmer-than-normal month for Greece, with the average temperature estimated to be around 2–3°C above climatic averages, according to protothema.gr meteorologist Giorgos Tsatrafyllias.

As for rainfall, there appears to be a tendency toward above-normal precipitation, particularly in western Greece, while the signal for the rest of the country is considerably weaker, with no significant deviations from normal levels.

What the Models Show for October

For October, the Copernicus C3S multi-model seasonal forecast, which combines forecasting systems from major meteorological centers including ECMWF, the Met Office, Météo-France, DWD, CMCC, NCEP, JMA, ECCC and BOM, indicates temperatures in Greece above normal levels.

At the same time, lower atmospheric pressure over the region favors more disturbances, with a tendency toward increased rainfall mainly in central and southern Greece. In northern Greece, the signal for increased precipitation is weak or nonexistent.

Overall, therefore, October appears likely to be warmer than normal and wetter, particularly in the central and southern parts of the country.

Seasonal models do not forecast the weather on a specific day. Instead, they attempt to estimate weather trends over one or more months—that is, whether a given period is more likely to be warmer, colder, drier or wetter than normal.

They are based on numerous different scenarios, or ensembles, which is why their forecasts are probabilistic rather than certain.

The margin of uncertainty increases the farther ahead we look in time, while reliability varies considerably depending on the region and the parameter being forecast. In Europe, in particular, it is not appropriate to assign them a single overall percentage of accuracy.

They are generally more useful for identifying large-scale patterns and broad trends, while rainfall forecasts typically carry greater uncertainty than temperature forecasts.