Strong rainfall and thunderstorms are expected on Wednesday, October 28, according to meteorologist Theodoros Kolydas, with Thessaly, Evia, the Sporades, and other areas of central and eastern Greece facing the threat of severe weather events. Kolydas is urging the public to exercise heightened caution, as forecast models agree on the likelihood of significant rainfall, though they diverge considerably in their estimates of intensity. The National Meteorological Service (EMY) has issued a red warning for five regions, while Civil Protection has placed a series of regional units and regions on Red Code alert. The severe weather coincides with the national holiday parades and celebrations, making travel conditions a particular concern.
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Kolydas: Major divergences in forecast models for October 28
In a post on social media, Theodoros Kolydas presented data from three major numerical weather models — ICON-EU, ECMWF, and GFS — explaining that while all three agree on the probability of heavy rainfall, they differ significantly in their estimated totals. ICON-EU shows the most extreme scenario, forecasting a maximum daily rainfall of 249.8 mm in Thessaly. The European ECMWF model puts the maximum at 102.8 mm for the same region, while the American GFS model is considerably more conservative, estimating a maximum of just 48.4 mm.
The gap between the three forecasts is substantial and reflects genuine uncertainty about the exact severity of the storm system. The 249.8 mm figure is a projection from one specific model and does not mean that such amounts will necessarily fall across all of Thessaly. The final distribution of rainfall will depend on how the weather system evolves and what updated forecast data shows.
⚠️⚠️ΣΥΓΚΛΙΣΕΙΣ ΚΑΙ ΑΠΟΚΛΙΣΕΙΣ ΑΡΙΘΜΗΤΙΚΩΝ ΜΟΝΤΕΛΩΝ – ΔΩΣΤΕ ΒΑΣΗ ΣΤΟΥΣ ΣΥΝΑΓΕΡΜΟΥΣ ΠΟΥ ΕΚΔΙΔΟΝΤΑΙ ΑΠΟ ΤΗΝ ΕΜΥ Ιδιαίτερο ενδιαφέρον παρουσιάζει η εξέλιξη του καιρού την Τετάρτη 28 Οκτωβρίου, ανήμερα της εθνικής επετείου, καθώς τα τρία μεγάλα προγνωστικά μοντέλα, ICON-EU, ECMWF και GFS, αποτυπώνουν την πιθανότητα σημαντικών βροχοπτώσεων, κυρίως στην κεντρική και ανατολική ηπειρωτική χώρα. Ωστόσο, οι διαφορές τους ως προς την ένταση των φαινομένων είναι ιδιαίτερα μεγάλες. 📌Το ICON-EU εμφανίζει ένα εξαιρετικά ισχυρό σήμα βροχόπτωσης στη Θεσσαλία, με το μεγαλύτερο προβλεπόμενο 24ωρο ύψος στην ελληνική επικράτεια να φτάνει τα 249,8 mm. 📌Το ECMWF δίνει επίσης σημαντικές βροχοπτώσεις, αλλά αισθητά χαμηλότερες, με μέγιστο στην Ελλάδα τα 102,8 mm, επίσης στη Θεσσαλία. 📌Αντίθετα, το GFS είναι αρκετά πιο συγκρατημένο, περιορίζοντας το αντίστοιχο μέγιστο στα 48,4 mm. Παρά τις αποκλίσεις, το κοινό στοιχείο των προγνώσεων είναι ότι η Τετάρτη απαιτεί αυξημένη μετεωρολογική προσοχή, ιδιαίτερα στη Θεσσαλία. Η εξέλιξη αποκτά ακόμη μεγαλύτερη σημασία επειδή συμπίπτει με τις εορταστικές εκδηλώσεις και τις μετακινήσεις της 28ης Οκτωβρίου. ⚠️Η ανησυχία ενισχύεται από το σημερινό έκτακτο δελτίο της ΕΜΥ, το οποίο προβλέπει κόκκινη προειδοποίηση για την Τετάρτη στη Μαγνησία, την περιοχή της Λάρισας, τις Σποράδες, την Εύβοια και τα Δωδεκάνησα. Πορτοκαλί προειδοποίηση ισχύει για περιοχές της ανατολικής Στερεάς, της Αττικής και του ανατολικού Αιγαίου. @CivPro_GR
— Theodoros Kolydas (@KolydasT) October 26, 2026
“Pay attention to the alerts issued by the National Meteorological Service”
The meteorologist stresses that the public should follow official EMY warnings rather than focusing solely on the raw figures from any single model. His post, titled “Convergences and divergences in numerical models — pay attention to the alerts issued by EMY,” underscores that the overall picture demands a heightened level of caution.
“Despite the divergences, the common thread across all forecasts is that Wednesday calls for increased meteorological vigilance, particularly in Thessaly,” he wrote. The timing of the severe storms adds an extra layer of concern, as October 28 is Greece’s national holiday — “Ohi Day” — when student and military parades are held across the country and road traffic is significantly higher than usual.
The five regions under red warning from EMY
According to the Special Bulletin for Dangerous Weather Phenomena issued on Monday, October 26, the National Meteorological Service has placed Magnesia, Larissa, the Sporades, Evia, and the Dodecanese under red warning. In Magnesia and Larissa, severe conditions are expected to continue through late at night, while in the Sporades and Evia they are forecast to last through late evening. The Dodecanese is also under red warning, with the risk of heavy rain, thunderstorms, and localized hailstorms.
An orange warning has been issued for eastern Central Greece, primarily Phthiotis and Boeotia, where intense weather events are expected intermittently through late night. In Attica, heavy rainfall and thunderstorms are forecast from the early morning hours through midday on Wednesday, while the orange warning for the eastern Aegean islands remains in effect through late evening.
Red Code status in effect through October 29
The General Secretariat for Civil Protection has placed the regional units of Evia, Phthiotis, Boeotia, the Sporades, Magnesia, Larissa, and the Dodecanese, as well as the regions of Attica and North Aegean, on Red Code mobilization status from Monday, October 26 through Thursday, October 29. The measure mandates heightened operational readiness from all relevant services, ensuring they can respond swiftly to any problems caused by the heavy rainfall and storm activity.
