If you plan to visit Seattle in September, the weather is typically alright, with an average high temperature of +70°F during the day and approximately 7 sunny days. Expect some rainy, though, as there are typically 13 rainy days in the month and around 62 mm of precipitation. The weather is changeable so you may have to pack for every eventuality. Search flightsin one click on Avionero.
Average weather
☀️
+70°F
Avg. max. temperature
+41°F
Min.
+91°F
Max.
62 mm
Total precipitation
76%
Avg. humidity
1 m/s
Avg. wind
7 ☀️
Sunny Days
10 ⛅️
Cloudy
13 🌦
Rainy
Our opinion: Seattle has OK weather in September.
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Average temperature in Seattle in September
Here are the expected maximum, average and minimum temperatures in Seattle for September based on the historical data.
Last Year
Historical Data
Going from a maximum of +84°F during the day to a minimum of +48°F during the night, the temperature in September averages around +72°F.
The average maximum temperature goes down 45% by the end of the month, compared with the beginning of the month, from +75°F to +59°F.
Is Seattle warm or cold in September?
Seattle is typically mild in September.
Maximum temperatures go down compared to the previous month from +75°F to +70°F. The minimum temperature also goes down from +57°F to +54°F.
Pack a light jacket as it will be warm in the day and cool in the evenings.
September is one of the warmest months in Seattle, here is the comparison with other months:
Water temperature in Seattle in September
Water in Seattle in September is Cold. It varies from +52°F to +55°F, with an average of +53°F.The air temperature averaging +70°F is higher than the water temperature.
The water temperature in September is one of the warmest of the entire year:
The warmest water temperatures in Seattle are reached in August, when the average sea temperature rises to +53°F. The coldest water temperatures are in February, with an average of +45°F.
Can you swim in Seattle in September?
We would not recommend swimming in Seattle in September, the water is very cold (+53°F on average). Consider swimming only if you are an experienced cold-water swimmer with proper gear.
🦭
Cold
Below +61°F
🏄♂️
Fresh
61°F - 70°F
🏊
Comfortable
70°F - 77°F
👙
Warm
77°F - 82°F
🔥
Very warm
+82°C and up
You will need a full-body wetsuit, cap, gloves, a warm change of clothes, and a hot drink ready for after your swim.
Travel to Seattle
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✈️
0
Flights per week
$343
Min. Price
$343
Max. Price
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Climate in Seattle in September
Seattle weather looks like this, on average, in September and the surrounding months.
August
September
October
Avg. temperature
+75°F
+70°F
+59°F
Min. temperature
+46°F
+41°F
+32°F
Max. temperature
+97°F
+91°F
+84°F
Rainfall
29 mm
62 mm
114 mm
Wind
1 m/s
1 m/s
2 m/s
Avg. water temperature
+53°F
+53°F
+51°F
Humidity
71%
76%
82%
Air pressure
1015 HPa
1015 HPa
1016 HPa
Sunny days
9
7
3
Cloudy days
13
10
10
Rainy days
9
13
18
Snowy days
0
0
0
September typically has worse weather conditions compared to August.It’s getting colder in September. From +75°F in the day, the average maximum temperature lowers to +70°F.Prepare for more rain. Average rainfall goes from 29 mm to 62 mm.Humidity rises from 71% to 76%.The average wind speed doesn’t change much during September, staying around 1 m/s.The days becoming less sunny, going from 9 sunny days in August to 7 in September.
October brings much the same weather, it remains ok.
Wind speed in Seattle in September based on historical data.
Last Year
Historical Data
The average wind speed is 1 m/s getting up to 3 m/s which is a light breeze; barely moving the tree leaves.
The average wind speed in Seattle is gradually increasing during September, going from 2 m/s to 2 m/s over the course of the month.
Rain
Amount of rainfall in mm during September in Seattle based on historical data.
Last Year
Historical Data
Typically, there is a 43% chance of rain on an average day in September, with total rainfall of approximately 145 mm. The maximum amount of rainfall per day is around 29 mm, which is moderate rain.September is a pretty wet month with over 13 rainy days, so don’t forget to pack an umbrella, raincoat, and a pair of wellies.
Here’s how September is compared with other months in the amount of precipitation, total mm:
Seattle wettest month is November, where a typical day has a 70% chance of precipitation and 177 mm of rainfall per day. July, on the other hand, is the driest month with a mere 29% chance of precipitation and 28 mm of rainfall per day.
How was the weather last September in Seattle?
This is the weather in Seattle in September 2023:
1 September
☁️
+75°F
2 September
☀️
+83°F
3 September
☁️
+83°F
4 September
☁️
+66°F
5 September
☁️
+70°F
6 September
☁️
+74°F
7 September
☁️
+73°F
8 September
☀️
+73°F
9 September
☀️
+78°F
10 September
☀️
+79°F
11 September
☁️
+79°F
12 September
☁️
+70°F
13 September
☁️
+72°F
14 September
☀️
+76°F
15 September
☀️
+80°F
16 September
☀️
+79°F
17 September
☁️
+76°F
18 September
☁️
+69°F
19 September
☁️
+66°F
20 September
🌧️
+65°F
21 September
☀️
+67°F
22 September
☀️
+77°F
23 September
☁️
+75°F
24 September
☁️
+63°F
25 September
🌧️
+60°F
26 September
🌧️
+61°F
27 September
🌧️
+57°F
28 September
🌧️
+61°F
29 September
☁️
+57°F
30 September
☁️
+60°F
In September 2023 Seattle had 9 sunny days, 16 cloudy days, and 5 rainy days. The average maximum temperature was +72°F, with an absolute maximum of +84°F and a minimum of +57°F. The average humidity was 78%, with a maximum of 100% and a minimum of 48%. The average wind speed was 1 m/s, with a maximum of 6 m/s and a minimum of 0 m/s.
Are you planning a trip in September?
Climate Change Over the Years
This is how Seattle climate has changed over the last 43 years.
The climate in Seattle in September has not changed that much over the last 43 years.
The average temperature was the lowest in 2011 (+57°F) and the highest in 2014 (+62°F). The driest year was 1985 with only 714 mm of rainfall, and the wettest year was 2021 with 2549 mm.
FAQ
Frequently asked questions about the weather in Seattle in September:
Is September a good time to visit Seattle?
It’s always a good time to visit Seattle, but the weather is changeable in September, so plan a mix of indoor and outdoor activities and exploring, and pack for every eventuality.
Can you sunbathe in Seattle in September?
September has mild temperatures in Seattle. Not ideal for sunbathing, but still good for daytime outdoor activities, but plan for cool evenings. Pack a light jacket and shorts!
Can you swim in Seattle in September?
Swimming in Seattle in September is challenging and not recommended for inexperienced swimmers or without proper equipment and preparation.
Is Seattle rainy in September?
Seattle is often rainy in September. You may get a bit damp when outside, so pack an umbrella, and maybe even a raincoat.
Is it sunny in Seattle in September?
Usually, it’s not very sunny in Seattle in September, often it’s pretty cloudy. Pack for any eventuality; layering can help reduce the number of bulky items needed.
How much does it cost to fly to Seattle in September?
The normal prices to fly to Seattle is $343 - $343. It means that the majority of our users have picked flights in this range. To find the best price we recommend you search early, using our flexible dates feature.
For this page, we’ve looked at the typical weather in Seattle, based on historical hourly weather data from January 1, 1979, to December 31, 2023.
For past dates, we show actual recorded data at the location at that time. Forecasts are based on recorded weather during that day of the year, averaged over the total years for which we have records (unless stated otherwise). The daily temperature is the highest recorded temperature in the shadow during that day.
