The Hellenic National Meteorological Service (HNMS) has released its seasonal outlook for summer 2025, indicating a particularly warm and dry summer for large parts of Greece and Europe. The forecast is signed by Panagiotis Skrimizeas and Anastasia Papakrivou, two senior meteorologists of the HNMS, and is based on data from major European and multi-model climate forecasting systems.
Above-Normal Temperatures and Reduced Rainfall in Northern Greece
According to the report, the June–August 2025 period is expected to bring higher-than-average temperatures across most of Greece. In Macedonia, Thrace, and northern Thessaly, temperatures are likely to be 1 to 2°C above normal, while rainfall in those same regions is also expected to be below seasonal averages.
This trend aligns with the broader European outlook, with high pressure systems expected to dominate much of the continent, increasing the likelihood of heatwaves and dry spells.
Agreement Between ECMWF and Multi-Model Systems
The forecast relies on two major sources:
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The European Centre for Medium-Range Weather Forecasts (ECMWF), which predicts widespread positive temperature anomalies throughout Europe.
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The Copernicus Multi-Model System (C3S), which supports this outlook and even points to more intense warming in certain regions.
Both models strongly agree on a warmer-than-average summer for Greece, particularly in the north and northeast. They also suggest that rainfall will likely be below normal in those same regions.
High Pressure Dominance and Potential for Aegean Winds
Forecast charts at the 500 hPa level (mid-troposphere) show a dominance of high-pressure systems over Europe, pointing toward stable, warm weather patterns.
The ECMWF model also supports the possibility of persistent “etesian” northerly winds (commonly known as the Meltemi) over the Aegean Sea, which can offer moderate cooling effects, whereas the multi-model system is less conclusive.
Oceanic Oscillations: Neutral NAO, Uncertain El Niño
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North Atlantic Oscillation (NAO): Expected to remain in a neutral phase, suggesting limited influence on summer weather in Europe.
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El Niño / ENSO: A weak El Niño phase may develop during the summer, but uncertainty remains high about its potential impact.
Key Takeaway: Hotter and Drier Summer Ahead for Greece
With strong agreement between forecasting systems, the summer of 2025 is shaping up to be one of the warmest in recent years, especially for northern Greece, which may also experience drier-than-average conditions.
Authorities and the public are advised to stay alert for heatwaves, ensure preparedness for wildfire risk, and take precautions during extreme temperature events.
