Click on a day for an hourly weather forecast
The temperatures in Oswego in September are comfortable with low of 14°C and and high up to 24°C.
You can expect about 3 to 8 days of rain in Oswego 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 Oswego in September 2025.
If you’re planning to visit Oswego in the near future, we highly recommend that you review the 14 day weather forecast for Oswego before you arrive.
| Month | Temperatures | Rainy Days | Dry Days | Snowy Days | Rainfall | Weather | More details |
|---|---|---|---|---|---|---|---|
| January | -2° / -8° | 5 | 11 | 15 | 84 mm | Awful | Oswego in January |
| February | 0° / -7° | 4 | 12 | 13 | 87 mm | Awful | Oswego in February |
| March | 8° / 1° | 7 | 17 | 6 | 116 mm | Awful | Oswego in March |
| April | 14° / 5° | 9 | 19 | 2 | 163 mm | Bad | Oswego in April |
| May | 21° / 12° | 10 | 21 | 0 | 207 mm | Ok | Oswego in May |
| June | 26° / 17° | 10 | 20 | 0 | 225 mm | Good | Oswego in June |
| July | 28° / 19° | 9 | 22 | 0 | 178 mm | Good | Oswego in July |
| August | 27° / 18° | 8 | 23 | 0 | 158 mm | Good | Oswego in August |
| September | 24° / 14° | 5 | 25 | 0 | 113 mm | Perfect | Oswego in September |
| October | 17° / 8° | 7 | 24 | 0 | 138 mm | Ok | Oswego in October |
| November | 9° / 2° | 6 | 21 | 3 | 81 mm | Bad | Oswego in November |
| December | 2° / -3° | 6 | 15 | 10 | 84 mm | Awful | Oswego in December |