Click on a day for an hourly weather forecast
The temperatures in Seattle in September are comfortable with low of 11°C and and high up to 23°C.
You can expect about 3 to 8 days of rain in Seattle 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 Seattle in September 2025.
If you’re planning to visit Seattle in the near future, we highly recommend that you review the 14 day weather forecast for Seattle before you arrive.
| Month | Temperatures | Rainy Days | Dry Days | Snowy Days | Rainfall | Weather | More details |
|---|---|---|---|---|---|---|---|
| January | 8° / 2° | 12 | 17 | 2 | 103 mm | Awful | Seattle in January |
| February | 8° / 1° | 9 | 16 | 3 | 72 mm | Awful | Seattle in February |
| March | 11° / 3° | 9 | 21 | 1 | 80 mm | Bad | Seattle in March |
| April | 14° / 4° | 6 | 24 | 0 | 55 mm | Good | Seattle in April |
| May | 19° / 7° | 5 | 27 | 0 | 39 mm | Good | Seattle in May |
| June | 22° / 9° | 3 | 27 | 0 | 29 mm | Good | Seattle in June |
| July | 27° / 12° | 1 | 30 | 0 | 11 mm | Perfect | Seattle in July |
| August | 27° / 12° | 1 | 30 | 0 | 17 mm | Perfect | Seattle in August |
| September | 23° / 11° | 3 | 27 | 0 | 36 mm | Perfect | Seattle in September |
| October | 16° / 7° | 8 | 23 | 0 | 78 mm | Ok | Seattle in October |
| November | 10° / 4° | 10 | 19 | 0 | 97 mm | Bad | Seattle in November |
| December | 7° / 1° | 9 | 20 | 2 | 87 mm | Awful | Seattle in December |