September in Bismarck averages a daily high of 23.6°C with nights around 8.3°C. Expect roughly 7.2 wet days totalling 40.4mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Bismarck is May.
Based on BISMARCK MUNICIPAL AIRPORT, ND US (4.5km), 1995–2024. 30 years of September data.