Click on a day for an hourly weather forecast
The temperatures in Saint John in September are usually low and can range between 11°C and 18°C.
You can expect about 3 to 8 days of rain in Saint John 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 Saint John in September 2025.
If you’re planning to visit Saint John in the near future, we highly recommend that you review the 14 day weather forecast for Saint John before you arrive.
| Month | Temperatures | Rainy Days | Dry Days | Snowy Days | Rainfall | Weather | More details |
|---|---|---|---|---|---|---|---|
| January | -2° / -9° | 6 | 10 | 16 | 88 mm | Awful | Saint John in January |
| February | -2° / -8° | 5 | 8 | 15 | 77 mm | Awful | Saint John in February |
| March | 2° / -4° | 8 | 10 | 13 | 78 mm | Awful | Saint John in March |
| April | 7° / 1° | 8 | 17 | 5 | 79 mm | Awful | Saint John in April |
| May | 13° / 6° | 7 | 24 | 0 | 95 mm | Bad | Saint John in May |
| June | 17° / 10° | 6 | 24 | 0 | 95 mm | Good | Saint John in June |
| July | 21° / 14° | 4 | 27 | 0 | 75 mm | Good | Saint John in July |
| August | 22° / 14° | 3 | 28 | 0 | 63 mm | Good | Saint John in August |
| September | 18° / 11° | 4 | 26 | 0 | 72 mm | Good | Saint John in September |
| October | 13° / 7° | 5 | 25 | 0 | 83 mm | Ok | Saint John in October |
| November | 7° / 1° | 7 | 19 | 5 | 91 mm | Awful | Saint John in November |
| December | 1° / -4° | 7 | 13 | 11 | 110 mm | Awful | Saint John in December |