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
The beginning of September in Seattle brings a minor change in the average high-temperature, shifting from a warm 76.3°F (24.6°C) in August to an agreeable 69.6°F (20.9°C). Seattle in September experiences a low-temperature average of 50.5°F (10.3°C).Humidity
In September, the average relative humidity in Seattle is 75%.Rainfall
In Seattle, during September, the rain falls for 6 days and regularly aggregates up to 0.28" (7mm) of precipitation. In Seattle, during the entire year, the rain falls for 84.2 days and collects up to 5.2" (132mm) of precipitation.Snowfall
In Seattle, snow does not fall in April through October and December.Ocean temperature
In Seattle, the average seawater temperature in September is 53.2°F (11.8°C).Note: Dipping into 53.2°F (11.8°C) below 50°F (10°C) needs protective wear, or you'd face cold shock and breathing issues swiftly. Meanwhile, a slight swim around 55.4°F (13°C) feels cold to the bone.
Daylight
In Seattle, the average length of the day in September is 12h and 33min.On the first day of the month, sunrise is at 6:29 am and sunset at 7:49 pm. On the last day of September, sunrise is at 7:08 am and sunset at 6:49 pm PDT.
Sunshine
The average sunshine in September in Seattle, Washington, is 9.4h.UV index
In September, the average daily maximum UV index in Seattle is 4. A UV Index estimate of 3 to 5 represents a medium health hazard from unsafe exposure to UV radiation for the average person.Note: A daily maximum UV index of 4 in September translates into the following instructions:
Prioritize safety - The need to safeguard skin and eyes from harm is emphasized. Exposing oneself to the midday Sun can be harmful due to the strong UV radiation; limit your time outside. In bright sunlight, prioritize sunglasses that grant protection from UVA and UVB radiation.
Frequently asked questions
What are the temperatures in Seattle in September?
What is the average humidity in September in Seattle?
How much does it rain in Seattle in September?
When it does not snow in Seattle?
How cold is the water in September in Seattle?
How many hours of daylight does Seattle have in September?
What time are sunrise and sunset in September in Seattle?
How many hours of sunshine does Seattle have in September?
What is the UV index reading 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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