Click on a day for an hourly weather forecast
The temperatures in Janesville 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 Janesville 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 Janesville in September 2025.
If you’re planning to visit Janesville in the near future, we highly recommend that you review the 14 day weather forecast for Janesville before you arrive.
| Month | Temperatures | Rainy Days | Dry Days | Snowy Days | Rainfall | Weather | More details |
|---|---|---|---|---|---|---|---|
| January | -3° / -11° | 8 | 18 | 5 | 48 mm | Awful | Janesville in January |
| February | -1° / -10° | 7 | 16 | 5 | 46 mm | Awful | Janesville in February |
| March | 7° / -2° | 7 | 20 | 4 | 72 mm | Awful | Janesville in March |
| April | 13° / 3° | 8 | 21 | 1 | 114 mm | Bad | Janesville in April |
| May | 20° / 10° | 9 | 22 | 0 | 115 mm | Ok | Janesville in May |
| June | 25° / 15° | 9 | 21 | 0 | 138 mm | Good | Janesville in June |
| July | 27° / 18° | 7 | 24 | 0 | 96 mm | Good | Janesville in July |
| August | 26° / 17° | 8 | 24 | 0 | 92 mm | Good | Janesville in August |
| September | 23° / 13° | 6 | 24 | 0 | 90 mm | Perfect | Janesville in September |
| October | 15° / 6° | 8 | 23 | 0 | 91 mm | Ok | Janesville in October |
| November | 7° / 0° | 6 | 23 | 1 | 58 mm | Ok | Janesville in November |
| December | 1° / -6° | 8 | 20 | 3 | 61 mm | Awful | Janesville in December |