Normal weather for Seattle in September
It's pleasantly warm in September in Seattle with an average temperature of 22°C. Temperatures this month range from a low of 19°C to a high of 25°C. At night, you can expect temperatures between 12°C and 16°C.
In September, there is an average of 34 mm of precipitation, spread over 6 days. The wind speed is around 3 Bft, mostly coming from the Southwest.
Seattle in September |
New York | ||
|---|---|---|---|
 Average Temperature |
22°C | 27°C | |
 High Temp |
25°C | 31°C | |
| Low Temp |
19°C | 21°C | |
 Total Precipitation |
34 mm | 57 mm | |
| Rainy Days |
6 days | 9 days | |
Start of September
The month of September starts in Seattle with warm temps, averaging around 25°C during the day and nights around 15°C. There’s little chance of precipitation. The weather’s mostly sunny and dry.
With the temperature difference between day and night, it’s smart to wear layers. A T-shirt, light pants or skirt, and a light jacket are great for the day. For the evening and morning, a shirt, maybe a light sweater, and thin pants are recommended.
Mid September
By mid-September, daytime temps drop to around 22°C, with nights around 14°C. Not much precipitation expected during this period. It’s mostly dry and sunny.
Since it cools down at night, it’s a good idea to wear layers. A T-shirt, light pants or skirt, and a light jacket are great for the day. In the evening and morning, choose a light jacket, sweater or hoodie, and long pants.
End of September
By the end of September, the average daytime temperature in Seattle is around 21°C, while nighttime temps are about 13°C. A shower might pop up, but overall, the weather will be dry and sunny.
Because temperatures drop in the evening, wearing layers is recommended. During the day, a shirt, maybe a light sweater, and thin pants will do. In the evening and morning, choose a light jacket, sweater or hoodie, and long pants.
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Water temperature
The water temperature at Seattle is 16°C this month. This is probably too cold to swim without protective gear.
UV index
The UV index is a maximum of 7 this month. That's a moderate to high value on the intensity scale of 1 to 11. Unprotected skin can burn within 15-25 minutes.
Is September a good time to visit Seattle?
Looking for great weather? September is a good time to be in Seattle. The temperatures are nice, and there’s not too much rain.
Temperature records for Seattle in September
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Daily Temperature in September in Seattle
This chart shows the average daily high and low temperatures in September for Seattle, in degrees Celsius. The red line represents the highs, and the blue line shows the lows. The days of the month are displayed at the bottom of the chart. The data, based on historical observations, provide the average temperatures for this month.
Daily Precipitation in September in Seattle
The chart below shows the average daily precipitation in September for Seattle, measured in millimeters over the past few years. Precipitation is always measured as water, even if it’s snow or hail. The days of the month are listed at the bottom of the chart.
A low average precipitation means that the chance of rain on that day is usually small, while a higher average suggests that it rained more often. But remember, it’s just an average, and every day can be different. Based on historical weather data for September, you can expect about 6 days of precipitation in Seattle.
Daily UV Index in September in Seattle
This chart shows the average daily UV index in September in Seattle, with the UV index ranging from 0 to a maximum of 11. The bottom of the chart shows the days of the month. Based on historical data, this chart provides an idea of the daily UV radiation levels you can expect.
Temperature in September in Seattle Over the Years
This chart shows the average temperature in September in Seattle, measured in degrees Celsius, over the past few years.
Total Precipitation in September in Seattle Over the Years
This chart shows the average precipitation in September in Seattle, measured in millimeters over the past years. Precipitation is always measured as water, whether it’s snow or hail.
Daily Climate in September for Seattle
Click on any day in September to get detailed info about the usual weather on that day in Seattle. Check out the historical temperatures and precipitation over the past 10 years on this day.
Weather experiences in September in Seattle
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Average Weather in Seattle by Month
Click on a month below to see detailed weather info for Seattle. Based on historical weather data, you can see the average temperature, precipitation, wind, and UV index for each day of the month.
