Weather: strong warm episode from 23 August

A warning about a strong and relatively prolonged warm episode was issued on Tuesday 18 August 2026 by the meteorologist and former director of the National Meteorological Service (EMY) Thodoris Kolydas, in a post on social media. As he wrote, “the country is heading towards a strong and relatively prolonged warm episode, with temperatures around 4–6°C higher than normal for the season”. In his view this is “a clear warm anomaly and not simply the usual high temperatures of August”. The warming is expected from the second half of the week, with the hottest window placed between 23 and 26 August and the critical period on the 24th and 25th of the month.

As for individual cities, the estimates differ depending on the forecast model. In Athens around 38 degrees are forecast by the European ECMWF and 39 to 40 by the American GEFS. In Thessaloniki the forecast is for 36 to 37 degrees, up from 32 to 33 at current levels. In Larissa, because of its inland position, values range from 37 to 38 degrees in the ECMWF to 40 to 41 in the hottest scenario, while in Patras they range from about 37 to close to 40. The minimum temperatures are particularly significant, reaching 28 to 29 degrees in Athens and Patras: “The very high night-time temperatures do not allow any substantial easing of the heat burden during the night”, he noted.

The meteorologist himself is cautious about what to call the phenomenon. “On present data it would be preferable for us still to be restrained about the term ‘heatwave’”, he said, explaining that there is no certainty as to whether values of 40 degrees and above will acquire wide geographical extent and duration. As he clarified, there will be stronger arguments for calling it a heatwave if scenarios with 38 to 40 degrees or higher temperatures for several consecutive days are maintained. The GEFS appears generally hotter than the ECMWF, which keeps a milder scenario without cancelling out the strong warm trend.

The difference between the models also explains the discrepancies appearing in press reports: the figure of 41 degrees concerns Larissa alone and only in the hottest scenario, while generalisations about temperatures in the forties across the whole country do not follow from the post itself. By Tuesday evening no emergency bulletin or warning from EMY connected with the episode had been issued. The increased heat burden, especially with night-time temperatures close to 29 degrees, mainly affects the elderly, people with chronic conditions and those who work outdoors. More on the weather in the relevant section.