Seattle Weather in September
September in Seattle averages 22°C (72°F) during the day and 12°C (54°F) at night. The excellent conditions and moderate rainfall make it a solid month to visit.
Rainfall in Seattle in September
Analyzing past climate data, one can expect approximately 9 days of rain, averaging 49 mm (1.9 in). A fairly balanced picture this month, some wet days but nothing too extreme in terms of intensity.
Temperature in Seattle in September
Weather in Seattle is at its excellent in September. Highs reach 22°C (72°F), while nights settle around 12°C (54°F). September is part of the summer season. Conditions are often most pleasant around the middle of the day. Nights drop to around 12°C (54°F), which is noticeably cooler than the daytime. A light jacket for the evening is a sensible addition, and the cool nights tend to make sleeping comfortable.
Sunshine in Seattle in September
Expect a lot of sunshine this month, with about 220 hours of sun. These sunny conditions add to the overall experience.
Wind Speed in Seattle in September
Wind speeds average 4 m/s (8 knots) during September. At this speed, expect moderate winds that can raise dust and move small branches. Since this is an average, some days have gentle light winds while others experience stronger breezes that are quite noticeable.If you're inclined towards comfortable temperatures and drier conditions, September is a good time to visit Seattle.
Check the conditions for any month of the year.
For a detailed overview over the year and the best time to visit the United States of America, check out our Seattle's climate page.
Seattle Temperature in September
Min Temperature
12°C (54°F)
Max Temperature
22°C (72°F)
Chance of Rain
31%
Precipitation
49 mm (1.9 in)
Rainy days
9 days
Humidity
73%
Windspeed
4 m/s (8 knots)
Sunshine
220 hours
Percentage Sunshine
59%
Daily Historical Temperatures
50-year average (1976-2025)
Based on our historical records, temperatures in Seattle typically drop from around 23°C (73°F) at the start of September to approximately 19°C (66°F) by the end. Nights are cool, with lows typically ranging from 11°C (52°F) to 13°C (55°F).
Average temperatures in September
Daily Historical Precipitation
50-year average (1976-2025)
Average daily rainfall for each day of the month based on long-term records.
Average precipitation in September
Historical weather for Seattle in September
Browse day-by-day weather records for Seattle spanning 51 years. Select any month and year to see actual temperatures, rainfall, and conditions recorded on each day.
Seattle historical weather extremes in September
Based on 49 years of weather observations (1976-2025), these are the most extreme conditions recorded in Seattle.
- The warmest day in September was on September 2, 1988, with a maximum of 37°C (99°F).
- On September 24, 1988, Seattle saw its coldest September day with temperatures maxing out at 11°C (52°F).
- The coldest night in September in Seattle was on September 23, 1996, with a minimum of 2°C (36°F).
Best Places in the United States of America in September
Find out more about the weather in the United States of America and which places have the best travel conditions in this month. See all of the United States of America in September →
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What to Wear in Seattle in September
Comfortable temperatures call for an easy wardrobe in September. Pack summer basics like t-shirts and shorts, but include a light jacket for cooler moments. A pair of comfortable walking shoes is essential. Wet weather is likely, so pack waterproof gear for multiple rainy days. You'll definitely want to pack sunglasses and sunscreen. There will be plenty of bright sunshine this month.What To Do in Seattle in September
We rated the following activities from 1 (least suitable) to 10 (best) to do.
Check the conditions for any month of the year.
For a detailed overview over the year and the best time to visit the United States of America, check out our Seattle's climate page.
Temperature Rainfall Sunshine Humidity Wind Speed
See the full Seattle climate overview or explore weather in the United States of America.
