December in Piraeus averages a daily high of 15.5°C with nights around 9.1°C. Expect roughly 8.2 wet days totalling 59.3mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Piraeus is April–May.
Based on HELLINIKON, GR (10.2km), 1995–2024. 19 years of December data.