Seattle Weather in September

What's the weather like in Seattle (Washington) in September 2025?

The climate in Seattle during September can be summarized as mild and reasonably dry.

September is in the fall / autumn in Seattle and is typically the 4th warmest month of the year. Daytime maximum temperatures average around 21°C (69°F), whilst at night 11°C (52°F) is normal.

Seattle weather averages (imperial / metric)
Daytime temperature 20.7°C 69.3°F
Nightly temperature 10.9°C 51.6°F
Average temperature 15.8°C 60.4°F
Daily sunshine 7.8 hrs
Avg rainfall 49 mm 1.9 ins
Rainy days 9 days
Sea temperature 12.8°C 55.1°F
Humidity 73%
Windspeed 11.9kph 7 mph

On average September is the 5th driest month of the year in Seattle with around 49mm 1.9 inches of rain making it a reasonably dry time to visit. This rainfall is typically spread over 9 days, although this may vary considerably.

On the flip side this corresponds to an average of 7.8 hours of sunshine per day.

September temperatures in Seattle

Seattle average temperature in September

September rainfall

Seattle average rain in September

September hourly sunshine

Seattle average rain in September

The data used in these monthly averages covers a period of over 100 years right up until last year. As such they are a valid prediction of what to expect for the weather in Seattle in September 2025.

Other monthly averages

Best places to visit in September

UV index Best time to go?

Beta

Current (hourly) weather 15 day forecast

Seattle weather stats

Seattle weather statistics
Hottest month: August 23.5°C 74.3°F
Driest month: July 21mm 0.8ins
Sunniest month: July 10.8hrs
Coldest month: January 7.2°C 45°F
Wettest month: December 151mm 5.9ins
Map showing location of Seattle (47.60621, -122.33207) Seattle map pin © Google

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