September in Florissant averages a daily high of 27.6°C with nights around 16.5°C. Expect roughly 7.1 wet days totalling 72.6mm. Comfortable conditions for being outdoors all day.
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 September data.