Verdict: Excellent month
Seattle Weather in September
September hits the sweet spot in Seattle — highs around 21°C (70°F), ideal for a full day on foot. Rain is occasional — about 8 wet days in a typical year. Overall, September is one of the best months of the year to be in Seattle.
Average high
21°C / 70°F
Average low
13°C / 55°F
Rain days
~8
Precipitation
61 mm
What to pack for Seattle in September
- Layers — t-shirts under a light jacket or sweater
- A packable rain shell or compact umbrella earns its space
- Comfortable walking shoes — every guide on this site assumes you'll use them
September against the rest of the year
Warmest in Seattle: Jul (25°C / 77°F) · Coolest: Jan (8°C / 46°F) · Wettest: Jan (~20 rain days)
8°
3°
Jan
8°
3°
Feb
10°
3°
Mar
13°
5°
Apr
17°
9°
May
21°
12°
Jun
25°
15°
Jul
25°
15°
Aug
21°
13°
Sep
15°
9°
Oct
10°
5°
Nov
8°
3°
Dec
Daily highs / lows in °C · bars show rain days per month · ERA5 climate normals (2020–2024)