September in Grand Forks averages a daily high of 21.6°C with nights around 9.1°C. Expect roughly 8.8 wet days totalling 59.3mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Grand Forks is May–September.
Based on GRAND FORKS UNIVERSITY NWS, ND US (4.8km), 1995–2024. 30 years of September data.