September in Hiroshima averages a daily high of 29.3°C. Expect roughly 9.3 wet days totalling 160.4mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Hiroshima is April–May.
Based on HIROSHIMA, JA (1.6km), 1995–2024. 20 years of September data.