September in Nagaoka averages a daily high of 26.6°C. Expect roughly 12.8 wet days totalling 154.1mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Nagaoka is May–June.
Based on NIIGATA, JA (54.8km), 1995–2024. 20 years of September data.