September weather forecast
Bellevue, WA

The scenic lakeside city of Bellevue, Washington
The scenic lakeside city of Bellevue, Washington

Weather in September

September, the first month of the autumn in Bellevue, is still a pleasant month, with an average temperature varying between 70°F (21.1°C) and 50°F (10°C).

Temperature

In Bellevue, the average high-temperature in September marginally drops from a warm 76.6°F (24.8°C) in August to an agreeable 70°F (21.1°C). In September, in Bellevue, the average low-temperature is 50°F (10°C).

Humidity

In Bellevue, the average relative humidity in September is 74%.

Rainfall

In Bellevue, in September, it is raining for 7.5 days, with typically 0.63" (16mm) of accumulated precipitation. Throughout the year, in Bellevue, there are 119.1 rainfall days, and 11.97" (304mm) of precipitation is accumulated.

Snowfall

In Bellevue, snow does not fall in April through October.

Daylight

In Bellevue, the average length of the day in September is 12h and 33min.
On the first day of September, sunrise is at 6:27 am and sunset at 7:50 pm. On the last day of the month, sunrise is at 7:06 am and sunset at 6:50 pm PDT.

Sunshine

In Bellevue, the average sunshine in September is 9.3h.

UV index

In Bellevue, the average daily maximum UV index in September is 4. A UV Index of 3 to 5 symbolizes a medium vulnerability from unsafe exposure to UV radiation for the average person.
Note: The average daily UV index of 4 in September transform into the following instructions:
Take precautions. Light skin individuals may get burned in less than 30 minutes. The solar radiation is most powerful near the mid-day, so the exposure to the direct Sun should be reduced accordingly. A wide-brim hat offers excellent sun protection for the eyes, ears, face, and neck. Sunglasses with UVA and UVB protection significantly reduce eye damage from sun exposure. Tightly woven, loose-fitting clothes provide additional protection from the Sun.
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FAQ

What is the temperature in September in Bellevue?

The average high-temperature, in September, in Bellevue, Washington, is 70°F (21.1°C), while the average low-temperature is 50°F (10°C).

What is the average humidity in September in Bellevue?

In September, the average relative humidity in Bellevue is 74%.

How many days does it rain in September in Bellevue?

In Bellevue, Washington, in September, during 7.5 rainfall days, 0.63" (16mm) of precipitation is typically accumulated.

When it does not snow in Bellevue?

April through October are months without snowfall in Bellevue.

What is the average length of the day in September in Bellevue?

In Bellevue, the average day length in September is 12h and 33min.

When is the sunrise / sunset in September in Bellevue?

In September, on the first day of the month, sunrise is at 6:27 am and sunset at 7:50 pm. On the last day of the month, in Bellevue, Washington, sunrise is at 7:06 am and sunset at 6:50 pm PDT.

How many hours of sunshine does Bellevue have in September?

In September, the average sunshine duration is 9.3h.

What is the UV index intensity in September in Bellevue?

In September, the average daily maximum UV index in Bellevue is 4. A UV Index estimate of 3 to 5 represents a medium health risk from exposure to Sun's UV rays.
Average humidity
Average rainfall days
Average snowfall
Average snowfall days
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in September
Bellevue, WA

Average temperature in September - Bellevue, WA
  • Average high temperature in September: 70°F

The warmest month (with the highest average high temperature) is August (76.6°F).
The month with the lowest average high temperature is December (42.8°F).

  • Average low temperature in September: 50°F

The month with the highest average low temperature is August (53.4°F).
The coldest month (with the lowest average low temperature) is February (34.5°F).

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Average pressure in September
Bellevue, WA

Average pressure in September - Bellevue, WA
  • Average pressure in September: 30.01"Hg

The month with the highest atmospheric pressure is January (30.1"Hg).
The month with the lowest atmospheric pressure is August (30"Hg).

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Average wind speed in September
Bellevue, WA

Average wind speed in September - Bellevue, WA
  • Average wind speed in September: 3.7mph

The windiest month (with the highest average wind speed) is March (5.1mph).
The calmest month (with the lowest average wind speed) is August (3.4mph).

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Average humidity in September
Bellevue, WA

Average humidity in September - Bellevue, WA
  • Average humidity in September: 74%

The month with the highest relative humidity is January (85%).
The month with the lowest relative humidity is July (69%).

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Average rainfall in September
Bellevue, WA

Average rainfall in September - Bellevue, WA
  • Average rainfall in September: 0.63"

The wettest month (with the highest rainfall) is December (2.01").
The driest month (with the least rainfall) is July (0.24").

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Average rainfall days in September
Bellevue, WA

Average rainfall days in September - Bellevue, WA
  • Average rainfall days in September: 7.5 days

The month with the highest number of rainy days is March (13.7 days).
The month with the least rainy days is August (4.1 days).

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Average snowfall in September
Bellevue, WA

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

The month with the highest snowfall is February (1.77").
The months with the least snowfall are April, May, June, July, August, September and October (0").

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Average snowfall days in September
Bellevue, WA

Average snowfall days in September - Bellevue, WA
  • Average snowfall days in September: 0 days

The month with the highest number of snowfall days is February (3 days).
The months with the least snowfall days are May, June, July, August, September and October (0 days).

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Average daylight in September /
Average sunshine in September
Bellevue, WA

Average daylight in September / Average sunshine in September - Bellevue, WA
  • Average daylight in September: 12h and 33min

The month with the longest days is June (Average daylight: 15h and 55min).
The month with the shortest days is December (Average daylight: 8h and 31min).

  • Average sunshine in September: 9h and 18min

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 12min).

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Average sunshine days in September
Bellevue, WA

Average sunshine days in September - Bellevue, WA
  • Average sunshine days in September: 20.5 days

The month with the most sunshine days is August (24.9 days).
The month with the least sunshine days is February (13.8 days).

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Average UV index in September
Bellevue, WA

Average UV index in September - Bellevue, 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).

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Average cloud cover in September
Bellevue, WA

Average cloud cover in September - Bellevue, WA
  • Average cloud cover in September: 34

The month with the most cloud cover is December (Cloud cover 56).
The month with the least cloud cover is August (Cloud cover 25).

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Average visibility in September
Bellevue, WA

Average visibility in September - Bellevue, WA
  • Average visibility in September: 6mi

The months with the highest visibility are May, June, July, August and September (6mi).
The months with the lowest visibility are January, February, March, April, October, November and December (5mi).

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