St Louis, Missouri weather in September

Averages from 2021–2025 (150 days of record).

Average high: 82°F
Average low: 62°F
Rainy days: ~8 per month
Total precipitation: 3.5 in
Warmest recorded: 96°F
Coldest recorded: 46°F

Expect September days in St Louis, Missouri to top out around 82°F and cool to about 62°F overnight, with roughly 8 days of measurable rain across the month. In recent years September has ranged from 46°F to 96°F.

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Current St Louis, Missouri forecast → · Historical data by Open-Meteo (ERA5).