Contents
- Weather in September
- Frequently asked questions
- Average temperature in September
- Average pressure in September
- Average wind speed in September
- Average humidity in September
- Average rainfall in September
- Average rainfall days in September
- Average snowfall in September
- Average snowfall days in September
- Average sea temperature in September
- Average daylight in September
- Average sunshine in September
- Average sunshine days in September
- Average UV index in September
- Average cloud cover in September
- Average visibility in September
Weather in September
Temperature
Seattle experiences a moderate temperature shift at the start of September, with average high-temperatures adjusting a bit from a warm 76.3°F (24.6°C) in August to a pleasant 69.6°F (20.9°C). During September, Seattle records an average temperature of 50.5°F (10.3°C) at night.Humidity
In Seattle, the average relative humidity in September is 75%.Rainfall
In September, in Seattle, the rain falls for 6 days. Throughout September, 0.28" (7mm) of precipitation is accumulated. Throughout the year, there are 84.2 rainfall days, and 5.2" (132mm) of precipitation is accumulated.Snowfall
In Seattle, snow does not fall in April through October and December.Ocean temperature
In Seattle, in September, the average water temperature is 53.2°F (11.8°C).Note: Swimming in 53.2°F (11.8°C) feels unbearing at 55.4°F (13°C) and can be life-risking below 50°F (10°C), causing breathing issues and cold shock, depending on a person's capacity.
Daylight
In September, the average length of the day is 12h and 33min.On the first day of September in Seattle, sunrise is at 6:29 am and sunset at 7:49 pm. On the last day of the month, sunrise is at 7:08 am and sunset at 6:49 pm PDT.
Sunshine
In September, the average sunshine is 9.4h.UV index
In September, the average daily maximum UV index is 4. A UV Index of 3 to 5 symbolizes a moderate health risk from unsafe exposure to UV radiation for ordinary individuals.Note: The UV index of 4 in September translates into these instructions:
Take heed. Individuals of lighter complexion can be burned in less than half an hour. The Sun is at its harshest during midday; protect yourself by staying in shaded areas and minimizing exposure. Safeguard your eyes, ears, and face from sun rays with the aid of a wide-brim hat.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What are September temperatures?
What is the average humidity in September?
How much does it rain in September?
When it does not snow?
How cold is the water in September?
What is the average length of the day in September?
When is the sunrise / sunset in September?
How long on average sun shines in September?
What is the UV index intensity in September in Seattle?
Average temperature in September
Seattle, WA
- Average high temperature in September: 69.6°F
The warmest month (with the highest average high temperature) is August (76.3°F).
The month with the lowest average high temperature is December (43.7°F).
- Average low temperature in September: 50.5°F
The month with the highest average low temperature is August (54°F).
The coldest month (with the lowest average low temperature) is December (35.1°F).
Average pressure in September
Seattle, WA
- Average pressure in September: 30.01"Hg
The month with the highest atmospheric pressure is January (30.1"Hg).
The months with the lowest atmospheric pressure are March, August and September (30.01"Hg).
Average wind speed in September
Seattle, WA
- Average wind speed in September: 3.9mph
The windiest month (with the highest average wind speed) is March (5.3mph).
The calmest months (with the lowest average wind speed) are July and August (3.5mph).
Average humidity in September
Seattle, WA
- Average humidity in September: 75%
The month with the highest relative humidity is January (85%).
The month with the lowest relative humidity is July (69%).
Average rainfall in September
Seattle, WA
- Average rainfall in September: 0.28"
The wettest month (with the highest rainfall) is December (0.87").
The driest months (with the least rainfall) are July and August (0.12").
Average rainfall days in September
Seattle, WA
- Average rainfall days in September: 6 days
The month with the highest number of rainy days is November (9.1 days).
The month with the least rainy days is August (2.8 days).
Average snowfall in September
Seattle, WA
- Average snowfall in September: 0"
The month with the highest snowfall is February (0.71").
The months with the least snowfall are April, May, June, July, August, September, October and December (0").
Average snowfall days in September
Seattle, WA
- Average snowfall days in September: 0 days
The month with the highest number of snowfall days is February (1.9 days).
The months with the least snowfall days are May, June, July, August, September and October (0 days).
Average sea temperature in September
Seattle, WA
- Average sea temperature in September: 53.3°F
The best month for swimming (with the highest average sea temperature) is August (53.5°F).
The coldest month (with the lowest average sea temperature) is February (45.3°F).
Average daylight in September /
Average sunshine in September
Seattle, WA
- Average daylight in September: 12h and 3min
The month with the longest days is June (Average daylight: 15h and 54min).
The month with the shortest days is December (Average daylight: 8h and 30min).
- Average sunshine in September: 9h and 2min
The month with the most sunshine is August (Average sunshine: 10h and 42min).
The month with the least sunshine is December (Average sunshine: 4h and 18min).
Average sunshine days in September
Seattle, WA
- Average sunshine days in September: 21.1 days
The month with the most sunshine days is August (25.9 days).
The month with the least sunshine days is November (16.8 days).
Average UV index in September
Seattle, WA
- Average UV index in September: 4
The month with the highest UV index is July (UV index 6).
The months with the lowest UV index are January, February, November and December (UV index 2).
Average cloud cover in September
Seattle, WA
- Average cloud cover in September: 33
The month with the most cloud cover is December (Cloud cover 56).
The month with the least cloud cover is August (Cloud cover 25).
Average visibility in September
Seattle, WA
- Average visibility in September: 6mi
The months with the highest visibility are April, May, June, July, August, September and October (6mi).
The months with the lowest visibility are January, February, March, November and December (5mi).
Seattle, Washington, USA
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