September in Basel averages a daily high of 21°C with nights around 11.2°C. Expect roughly 10.1 wet days totalling 68.1mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Basel is June–September.
Based on BASEL BINNINGEN, SZ (2.9km), 1995–2024. 30 years of September data.