September in Green Bay averages a daily high of 22.3°C with nights around 10.3°C. Expect roughly 8.3 wet days totalling 79.7mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Green Bay is May–September.
Based on GREEN BAY BOTANICAL, WI US (6.4km), 1995–2024. 22 years of September data.