May in Sankt Gallen averages a daily high of 3.4°C with nights around -1.2°C. Expect roughly 18 wet days totalling 237.2mm. A hard month to visit for comfort alone.
Across the year, the best time to visit Sankt Gallen is June–August.
Based on SAENTIS, SZ (19.4km), 1995–2024. 30 years of May data.