Click on a day for an hourly weather forecast
The temperatures in St. Louis in September are comfortable with low of 13°C and and high up to 23°C.
You can expect about 3 to 8 days of rain in St. Louis during the month of September. It’s a good idea to bring along your umbrella so that you don’t get caught in poor weather.
Our weather forecast can give you a great sense of what weather to expect in St. Louis in September 2025.
If you’re planning to visit St. Louis in the near future, we highly recommend that you review the 14 day weather forecast for St. Louis before you arrive.
| Month | Temperatures | Rainy Days | Dry Days | Snowy Days | Rainfall | Weather | More details |
|---|---|---|---|---|---|---|---|
| January | -1° / -7° | 6 | 8 | 17 | 104 mm | Awful | St. Louis in January |
| February | 1° / -6° | 6 | 7 | 15 | 104 mm | Awful | St. Louis in February |
| March | 8° / 0° | 9 | 13 | 9 | 131 mm | Awful | St. Louis in March |
| April | 14° / 5° | 10 | 17 | 3 | 161 mm | Bad | St. Louis in April |
| May | 21° / 12° | 10 | 21 | 0 | 179 mm | Ok | St. Louis in May |
| June | 25° / 16° | 9 | 21 | 0 | 184 mm | Good | St. Louis in June |
| July | 27° / 17° | 9 | 22 | 0 | 165 mm | Good | St. Louis in July |
| August | 26° / 16° | 7 | 24 | 0 | 138 mm | Good | St. Louis in August |
| September | 23° / 13° | 6 | 24 | 0 | 109 mm | Perfect | St. Louis in September |
| October | 17° / 8° | 6 | 24 | 1 | 120 mm | Good | St. Louis in October |
| November | 9° / 2° | 7 | 18 | 5 | 107 mm | Awful | St. Louis in November |
| December | 3° / -2° | 8 | 11 | 12 | 102 mm | Awful | St. Louis in December |