Seattle
Washington, USA
Long-term weather forecast
Long-term weather forecast

September weather forecast and climate
Seattle, WA

Beautiful dusk skyline over the giant skyscrapers of Seattle, Washington
Beautiful dusk skyline over the giant skyscrapers of Seattle, Washington
September is transitional month and experiences summer weather only for the first few weeks. With a significant rise in humidity to 72.9%, temperatures in September cool to the range of 51.8°F (11°C) and 68°F (20°C) as autumn arrives. With the close of summer, rainfall sets to rain for nine days gathering moderately low precipitation of 2" (50.8mm).
Swimming in the 55.4°F (13°C) seawater remains rampant throughout September, as does sunbathe in the seven hours of warm sunshine.

What is the temperature in Septiembre in Seattle?

The average high-temperature, in Septiembre, in Seattle, Washington, is 70.5°F (21.4°C), while the average low-temperature is 52.2°F (11.2°C).

What is the average humidity in Septiembre in Seattle?

In Septiembre, the average relative humidity in Seattle is 73.2%.

How much does it rain in Seattle in Septiembre?

In Septiembre, in Seattle, Washington, the rain falls for 7.9 days. Throughout Septiembre, 1.5" (38.1mm) of precipitation is accumulated.

When it does not snow in Seattle?

In Seattle, Washington, snow does not fall in Abril through Octubre.

What is the ocean temperature in Septiembre in Seattle?

In Seattle, Washington, the average seawater temperature in Septiembre is 53.2°F (11.8°C). Swimming in 53.2°F (11.8°C) is considered dangerous. Unprotected immersion in temperatures below 50°F (10°C) causes quickly maximum intensity cold shock with hyperventilation.

What is the average length of the day in Septiembre in Seattle?

In Septiembre, the average length of the day in Seattle is 12.5h.

How long on average sun shines in Septiembre in Seattle?

In Seattle, Washington, the average sunshine in Septiembre is 7.4h.

How high is the UV index in Septiembre in Seattle?

The average daily maximum UV index in Septiembre in Seattle, Washington, is 5. A UV Index of 3 to 5 symbolizes a medium health risk from unprotected exposure to the UV radiation.
Average temperature in September - Seattle, WA
  • Average high temperature in September: 70.5°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 (45.7°F).

  • Average low temperature in September: 52.1°F

The month with the highest average low temperature is August (55.9°F).
The coldest month (with the lowest average low temperature) is December (35.6°F).

Average humidity in September - Seattle, WA
  • Average humidity in September: 73.2%

The month with the highest relative humidity is December (80.1%).
The month with the lowest relative humidity is July (65.4%).

Average rainfall in September - Seattle, WA
  • Average rainfall in September: 1.5"

The wettest month (with the highest rainfall) is November (6.6").
The driest month (with the lowest rainfall) is July (0.7").

Average rainfall days in September - Seattle, WA
  • Average rainfall days in September: 7.9 days

The month with the highest number of rainy days is November (18.4 days).
The month with the lowest number of rainy days is August (4.8 days).

Average snowfall in September - Seattle, WA
  • Average snowfall in September: 0"

Months with the highest snowfall are February and December (1.7").
Months with the lowest snowfall are April, May, June, July, August, September and October (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 December (1.6 days).
Months with the lowest number of snowfall days are April, 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: 12.5h

The month with the longest days is June (Average daylight: 15.9h).
The month with shortest days is December (Average daylight: 8.5h).

  • Average sunshine in September: 7.4h

The month with most sunshine is July (Average sunshine: 10.1h).
The month with least sunshine is December (Average sunshine: 1.7h).

Average UV index in September - Seattle, WA
  • Average UV index in September: 5

Months with the highest UV index are June and July (UV index 7).
Months with the lowest UV index are January, November and December (UV index 1).