May in Piraeus averages a daily high of 25.8°C with nights around 16.1°C. Rain is rare — about 2.6 wet days and 10.4mm across the month. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Piraeus is April–May.
Based on HELLINIKON, GR (10.2km), 1995–2024. 23 years of May data.