September in Seongnam-si averages a daily high of 26.3°C. Expect roughly 21 wet days totalling 253.7mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Seongnam-si is June.
Based on SEOUL CITY, KS (20.8km), 1995–2024. 19 years of September data.