September in Oshkosh averages a daily high of 23°C with nights around 11.9°C. Expect roughly 9.2 wet days totalling 76mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Oshkosh is May–September.
Based on OSHKOSH, WI US (1.3km), 1995–2024. 30 years of September data.