The severe weather system Adel demonstrated once again that even 35–40 mm of rain can cause significant disruption in Attica. The downpour in Attica was short but intense, and the city’s limited absorption and drainage capacity was quickly overwhelmed.

Several streets briefly turned into water channels, while low-lying areas received runoff that the drainage network could not handle. The National Observatory of Athens/Meteo published a map showing which areas of Attica recorded the highest rainfall. By 09:00 on Friday morning, Faliro had registered the greatest accumulation. The areas with the highest rainfall were:

• Faliro: 52 mm

• Alimos: 50 mm

• Kifisia: 50 mm

• Aegina: 49 mm

• Ekali: 48 mm

• Peristeri: 41 mm

• Chaidari (forest): 40 mm

• Malakasa: 34 mm

High rainfall across the country

Meteo also released a map showing rainfall totals from Wednesday through Friday. According to the data, rainfall exceeded:

• 100 mm at 36 stations

• 80 mm at 63 stations

• 60 mm at 138 stations

Three stations in Epirus—specifically in the Tzoumerka region—recorded more than 200 mm, worsening an already difficult situation. Total rainfall for November in parts of Epirus has now surpassed 900–1,000 mm.

Areas with the highest rainfall between 26 and 28 November:

• Theodoriana, Arta: 231 mm

• Pramanta, Ioannina: 218 mm

• Artas Waterfall: 203 mm

• Lepiana, Arta: 193 mm

• Corfu: 169 mm

• Derviziana, Ioannina: 149 mm

• Pertouli, Trikala: 145 mm

• Vourgarelli, Arta: 139 mm

Why Attica flooded

Meteorologist Thodoris Kolydas commented on the flooding in Attica, noting that the issue was not just the volume of rain but the rate at which it fell—particularly dangerous in a densely built urban environment that acts as a “hard surface.” When large amounts of water reach the ground rapidly, they produce immediate surface runoff rather than slow absorption. With little exposed soil, water instead meets asphalt and concrete.

“According to data from the EAA/Meteo network, rainfall in the center of Athens reached 40 mm, while in areas such as Zografou and Goudi it reached 38–39 mm. These amounts were enough to overload critical parts of the road network, causing localized flooding, traffic delays, and minor inundations on streets unable to drain the water quickly. This once again highlights the chronic issue of rapid surface runoff in the Basin and the urgent need to upgrade drainage infrastructure,” he wrote.

Kolydas added that the episode underlines the importance of using all available warning tools:

“In a country where radar coverage has gaps and storms are developing more frequently and more intensely, operational response time becomes vital. With better use of satellite data and numerical models, issuing warnings 1–2 hours in advance is not only possible—it is necessary.”

Thodoris Kolydas’ full commentary (edited for clarity)

The double passage of thunderstorms over Attica — and what 40 mm of rain means

Yesterday we highlighted the likelihood of two successive waves of thunderstorms over Attica. Indeed, the first wave arrived late at night, followed by a second early in the morning, once again producing intense weather over the dense urban fabric of Athens.

Data from the EAA/Meteo network recorded rainfall reaching 40 mm in central Athens, and more than 38–39 mm in areas such as Zografou and Goudi. This alone caused localized flooding, traffic delays, and minor inundations on streets with limited drainage capacity.

It is not an exaggeration to say that Athens “flooded” from 40 mm of rain. In a heavily urbanized environment—with dense construction, channelized streams, and minimal absorption—even 40 mm is enough to cause problems. This comparison is important for understanding what 100 or 200 mm means in a region like Epirus, where rivers, aquifers, and mountainous basins are far more vulnerable to rapid flooding. If Attica struggles with 40 mm, imagine regions where rainfall is two to five times greater.

The issue of limited radar coverage — and operational needs

Attica, like much of the country, still has areas with inadequate radar coverage. This makes it difficult to assess rainfall intensity in real time and issue timely warnings. However, there are alternative tools—satellite products and predictive models—that can provide 1–2 hours of advance notice by detecting storm development and cloud-core intensification. These tools often identify the position and intensity of Mediterranean storms several hours before they occur.

Today’s weather event confirmed once more that even 35–40 mm of rain can cause major disruption in Attica. It also reminded us how critical early-warning systems are—especially as extreme weather becomes more frequent and intense. With better use of satellite products and models, issuing 1–2 hour warnings is entirely feasible and, in many cases, crucial.