May in Seongnam-si averages a daily high of 23.7°C. Expect roughly 13 wet days totalling 158.4mm. 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. 23 years of May data.