Click on a day for an hourly weather forecast
The temperatures in Sioux City in September are comfortable with low of 14°C and and high up to 25°C.
You can expect about 3 to 8 days of rain in Sioux City 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 Sioux City in September 2025.
If you’re planning to visit Sioux City in the near future, we highly recommend that you review the 14 day weather forecast for Sioux City before you arrive.
| Month | Temperatures | Rainy Days | Dry Days | Snowy Days | Rainfall | Weather | More details |
|---|---|---|---|---|---|---|---|
| January | -2° / -10° | 6 | 22 | 3 | 23 mm | Awful | Sioux City in January |
| February | 0° / -9° | 6 | 19 | 3 | 26 mm | Awful | Sioux City in February |
| March | 9° / -1° | 6 | 23 | 2 | 52 mm | Bad | Sioux City in March |
| April | 15° / 5° | 7 | 22 | 1 | 97 mm | Ok | Sioux City in April |
| May | 21° / 11° | 9 | 22 | 0 | 133 mm | Ok | Sioux City in May |
| June | 27° / 17° | 8 | 22 | 0 | 143 mm | Good | Sioux City in June |
| July | 30° / 19° | 6 | 25 | 0 | 80 mm | Good | Sioux City in July |
| August | 29° / 17° | 7 | 24 | 0 | 123 mm | Ok | Sioux City in August |
| September | 25° / 14° | 5 | 25 | 0 | 77 mm | Perfect | Sioux City in September |
| October | 17° / 7° | 5 | 25 | 0 | 64 mm | Good | Sioux City in October |
| November | 9° / 0° | 4 | 25 | 1 | 33 mm | Ok | Sioux City in November |
| December | 1° / -7° | 6 | 22 | 3 | 41 mm | Awful | Sioux City in December |