Locally heavy rain and storms are forecast from Monday afternoon until the morning of Tuesday in most parts of eastern Greece, according to the Emergency Report of Hazardous Weather Phenomena of the Hellenic Meteorological Service that is being constantly reviewed.
More specifically:

1. In the islands of the Cyclades from Monday afternoon until early Tuesday the phenomena will be severe -red warning-.
2. In the islands of eastern Aegean (mostly on Samos, Ikaria and Chios) from Monday night until Tuesday night
3. In eastern Sterea and the island of Evia from Monday night until Tuesday afternoon
4. In the region of Attica during the night 
5. In the region of Thessaly and the islands of Sporades from early Tuesday until Tuesday night
6. In the islands of the Dodecanese from Tuesday morning until Wednesday morning
7. In western and southern Crete from Tuesday night until the morning of Wednesday.