September in Lisbon averages a daily high of 26.3°C with nights around 17.8°C. Expect roughly 5.3 wet days totalling 36.8mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Lisbon is May–September.
Based on LISBOA GEOFISICA, PO (0.9km), 1995–2024. 25 years of September data.