Hottest (avg)
#3 / 12
Seattle in September
September weather, climate averages, and packing tips.
Avg High
Avg Low
Rain
Daylight 13h
What to expect
As autumn continues, September brings, where temperatures are dropping quickly. Daytime highs average 20°C / 69°F, dropping to 12°C / 53°F at night.
Skies are often changeable, and you should be prepared for regular rainfall (approx. 11 wet days).
September in context
How it compares to the rest of the year in Seattle.
Wettest (avg)
#9 / 12
Daylight Hours
#6 / 12
Windiest (avg)
#10 / 12
Highest UV
#6 / 12
Most Humid
#8 / 12
Temperature
- Daytime high
-
- Nighttime low
-
- Feels like (avg)
-
Sunshine
- Daylight
- 12.5 hours
- UV index (max)
- 6
- Typical sun hours
- 05:47 – 18:19
Rain & Snow
- Total
-
- Rainy days
- 11
- Cloud cover
- 52%
- Snowfall
-
Humidity & Wind
- Humidity (avg)
- 76%
- Wind (avg)
-
- Wind (max gusts)
-
Frequently asked questions
Is September a good time to visit Seattle?
Typical September days in Seattle reach highs of 20°C (68°F) with nights around 12°C (54°F). It usually feels mild by day and cool after dark. Overall, September sits in the middle of the Seattle climate range.
What are temperatures like in September?
Daytime temperatures in September typically peak near 20°C (68°F), while nights drop to around 12°C (54°F). Expect mild afternoons and cool evenings.
How much does it rain in September?
Rainfall in September averages 65 mm (2.6 in) across roughly 11 days. Overall it is a quite rainy time of year, so a light rain jacket and waterproof shoes are very handy.
How many hours of daylight are there in September?
You can expect about 13 hours of daylight in September. Sunrise is typically around 05:47 and sunset near 18:19. Daylight is fairly typical, with enough time for sightseeing.
Does the weather change during September?
September usually begins milder and cools down as the month goes on, so late-September can feel more like the next month.
How strong is the sun in September?
UV levels are moderate (around 6); sunscreen and sunglasses are still a good idea.
Is it windy in September?
In September, average wind speeds are around 8 km/h (5 mph), with gusts on the windiest days reaching about 43 km/h (27 mph). On the ground, it is it often feels breezy, especially in more exposed spots or along the coast.