September in Jōetsu averages a daily high of 27.2°C. Expect roughly 14.9 wet days totalling 207.1mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Jōetsu is May–June.
Based on TAKADA, JA (5.5km), 1995–2024. 24 years of September data.