December in St. Louis averages a daily high of 7.2°C with nights around -1.1°C. Expect roughly 8.4 wet days totalling 63.3mm. Demanding conditions — pack for it and plan indoor options.
Across the year, the best time to visit St. Louis is April–May.
Based on ST LOUIS SCIENCE CENTER, MO US (6.3km), 1995–2024. 20 years of December data.