Click on a day for an hourly weather forecast
The weather in Ontario in September is hot. The average temperatures are between 21°C and 31°C.
There shouldn't be any rainy days in in Ontario during September. Having said that, the days are very hot in September so hanging out outside is more recomanded during the after noons and evening time.
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 | 19° / 9° | 2 | 29 | 0 | 57 mm | Good | Ontario in January |
| February | 19° / 9° | 2 | 26 | 0 | 63 mm | Good | Ontario in February |
| March | 20° / 10° | 2 | 29 | 0 | 36 mm | Good | Ontario in March |
| April | 22° / 12° | 1 | 29 | 0 | 22 mm | Good | Ontario in April |
| May | 24° / 14° | 0 | 31 | 0 | 7 mm | Perfect | Ontario in May |
| June | 28° / 18° | 0 | 30 | 0 | 1 mm | Perfect | Ontario in June |
| July | 31° / 21° | 0 | 31 | 0 | 10 mm | Good | Ontario in July |
| August | 32° / 22° | 0 | 31 | 0 | 6 mm | Good | Ontario in August |
| September | 31° / 21° | 0 | 30 | 0 | 5 mm | Good | Ontario in September |
| October | 26° / 17° | 1 | 30 | 0 | 10 mm | Perfect | Ontario in October |
| November | 22° / 12° | 1 | 29 | 0 | 22 mm | Good | Ontario in November |
| December | 18° / 9° | 3 | 28 | 0 | 72 mm | Good | Ontario in December |