Click on a day for an hourly weather forecast
The temperatures in Williamstown in September are comfortable with low of 17°C and and high up to 25°C.
You can expect about 3 to 8 days of rain in Williamstown 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 Williamstown in September 2025.
If you’re planning to visit Williamstown in the near future, we highly recommend that you review the 14 day weather forecast for Williamstown before you arrive.
| Month | Temperatures | Rainy Days | Dry Days | Snowy Days | Rainfall | Weather | More details |
|---|---|---|---|---|---|---|---|
| January | 4° / -2° | 8 | 20 | 3 | 84 mm | Awful | Williamstown in January |
| February | 6° / -2° | 8 | 17 | 3 | 97 mm | Awful | Williamstown in February |
| March | 11° / 2° | 8 | 21 | 2 | 115 mm | Awful | Williamstown in March |
| April | 17° / 8° | 7 | 23 | 0 | 102 mm | Ok | Williamstown in April |
| May | 22° / 13° | 8 | 23 | 0 | 100 mm | Ok | Williamstown in May |
| June | 27° / 18° | 10 | 20 | 0 | 121 mm | Good | Williamstown in June |
| July | 30° / 21° | 11 | 20 | 0 | 124 mm | Ok | Williamstown in July |
| August | 29° / 21° | 10 | 21 | 0 | 135 mm | Ok | Williamstown in August |
| September | 25° / 17° | 7 | 23 | 0 | 106 mm | Good | Williamstown in September |
| October | 19° / 11° | 7 | 24 | 0 | 135 mm | Ok | Williamstown in October |
| November | 12° / 5° | 5 | 25 | 0 | 82 mm | Ok | Williamstown in November |
| December | 8° / 1° | 7 | 23 | 1 | 126 mm | Bad | Williamstown in December |