In the eastern Peloponnese town of Astros, a coastguard officer died after being struck by a wave while urging fishermen to leave the harbour.
Hours later, a woman was killed in the Athens suburb of Glyfada when floodwater pushed a car into her.
Winds topped 100 kilometres an hour in some areas, grounding ferries and forcing schools to close in Athens and parts of the west and south. Meteorologists said parts of the capital received the equivalent of six weeks of rain in a single day.
Authorities urged people to avoid travel, while Prime Minister Kyriakos Mitsotakis postponed an overseas trip as emergency crews dealt with flooded roads and damage.
