Click on a day for an hourly weather forecast
The temperatures in Ontario in September are comfortable with low of 15°C and and high up to 22°C.
You can expect about 3 to 8 days of rain in Ontario 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 Ontario in September 2025.
If you’re planning to visit Ontario in the near future, we highly recommend that you review the 14 day weather forecast for Ontario before you arrive.
| Month | Temperatures | Rainy Days | Dry Days | Snowy Days | Rainfall | Weather | More details |
|---|---|---|---|---|---|---|---|
| January | -2° / -7° | 6 | 9 | 17 | 54 mm | Awful | Ontario in January |
| February | -2° / -7° | 5 | 8 | 15 | 46 mm | Awful | Ontario in February |
| March | 4° / -2° | 7 | 15 | 9 | 63 mm | Awful | Ontario in March |
| April | 9° / 3° | 8 | 18 | 4 | 82 mm | Awful | Ontario in April |
| May | 16° / 9° | 7 | 24 | 0 | 100 mm | Ok | Ontario in May |
| June | 21° / 14° | 7 | 23 | 0 | 120 mm | Ok | Ontario in June |
| July | 25° / 19° | 7 | 24 | 0 | 128 mm | Good | Ontario in July |
| August | 25° / 19° | 5 | 26 | 0 | 114 mm | Perfect | Ontario in August |
| September | 22° / 15° | 5 | 25 | 0 | 74 mm | Good | Ontario in September |
| October | 15° / 9° | 7 | 23 | 0 | 88 mm | Ok | Ontario in October |
| November | 8° / 3° | 5 | 19 | 5 | 50 mm | Bad | Ontario in November |
| December | 2° / -2° | 7 | 11 | 13 | 52 mm | Awful | Ontario in December |