May in Barreiro averages a daily high of 22.9°C with nights around 14.5°C. Expect roughly 6.6 wet days totalling 49.8mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Barreiro is May–September.
Based on LISBOA GEOFISICA, PO (9km), 1995–2024. 26 years of May data.