December in Florissant averages a daily high of 7.3°C with nights around -1.6°C. Expect roughly 9.4 wet days totalling 64.5mm. Demanding conditions — pack for it and plan indoor options.
Across the year, the best time to visit Florissant is September–October.
Based on ST LOUIS LAMBERT INTERNATIONAL AIRPORT, MO US (6km), 1995–2024. 30 years of December data.