Seattle weather in September
Seattle in September averages 17°C (62°F) and 41 mm of rain.
Of the twelve months in Seattle, September is the third warmest and the fourth driest.
- Average temp
- 17°C (62°F)
12–22°C · 53–71°F
- Rainfall
- 41 mm
Not much rain
- Sunshine
- —
- Wind
- 11 km/h
What is Seattle like in September?
Daytime
Days are mild.
Rain
Rain is usually light.
Evening
Evenings are cooler. A layer helps after sunset.
What should I pack for Seattle in September?
A warm mid-layer
Nights drop to around 12°C (53°F).
September compared with August and October
September in Seattle is 2.8°C cooler than August and 16 mm wetter than it, which averages 19°C (67°F).
September in Seattle is 4.9°C warmer than October and 58 mm drier than it, which averages 12°C (53°F).
Daylight in Seattle in September
On 15 September the sun is up for 12 hours 32 minutes in Seattle, rising about 06:47 and setting about 19:20 local time.
September ends 1 hour 39 minutes shorter than it begins, so the last week of the month is a different length of day from the first.
That is 3 hours 26 minutes short of June, the longest-lit month here.
Where to stay in Seattle
Dates are a starting point for September.
Travel guides for Seattle
What to read before you book.
Seattle weather by month
TemperatureRainfall
How September compares with the rest of the year
September is highlighted. Every other month links to its own page.
| Month | Average | Rainfall |
|---|---|---|
| January | 6°C / 42°F | 147 mm |
| February | 6°C / 43°F | 96 mm |
| March | 8°C / 46°F | 106 mm |
| April | 10°C / 51°F | 81 mm |
| May | 14°C / 57°F | 48 mm |
| June | 16°C / 62°F | 37 mm |
| July | 19°C / 67°F | 15 mm |
| August | 19°C / 67°F | 25 mm |
| September | 17°C / 62°F | 41 mm |
| October | 12°C / 53°F | 99 mm |
| November | 8°C / 46°F | 160 mm |
| December | 5°C / 41°F | 147 mm |
Check another month
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FAQs about Seattle in September
September climate averages for Seattle, 1991–2020.
Seattle averages 17°C (62°F) in September, ranging from about 12°C (53°F) at night to 22°C (71°F) in the afternoon. That is a 1991–2020 average, so an individual week can run either side of it.
Barely. September sees only about 41 mm, so rain is unlikely to affect your plans.
Yes. September averages 17°C (62°F) against 12°C (53°F) in October — 4.9°C warmer.
September is 2.8°C cooler than August, and 16 mm wetter.
Yes. September falls inside the most comfortable stretch of the year here, May to October, on temperature and rainfall together.
This page does not show today's weather. It is a 1991–2020 climate normal from Meteostat — a long-run average of what September is usually like, which is what you want when booking months ahead. For today or the coming week, check a live forecast.
About 12 hours 32 minutes of daylight in mid-September, against 15 hours 58 minutes in June and 8 hours 27 minutes in December.
On 15 September, sunrise is about 06:47 and sunset about 19:20 local time. Both shift across the month — the month ends 1 hour 39 minutes shorter than it starts.
