September weather forecast
Snoqualmie Pass, WA

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Weather in September

In September, Snoqualmie Pass, Washington, witnesses a gradual shift from summer to fall. The weather begins to swing, showcasing shorter days and a noticeable plunge in temperatures. The transitional weather brings a slight increase in average rainfall, accompanied by a gradual increase in the degree of humidity. Further, the sunshine hours start to drop, predicting the impending arrival of winter. The month heralds the onset of fall, scattering beautiful autumn leaves throughout the city.

Temperature

September's onset corresponds with a shift in the average high-temperature, moving from an agreeable 71.2°F (21.8°C) in August to an enjoyable 62.1°F (16.7°C). Throughout the month of September, Snoqualmie Pass witnesses an average temperature of 41.2°F (5.1°C).

Humidity

In September, the average relative humidity in Snoqualmie Pass is 75%.

Rainfall

In Snoqualmie Pass, during September, the rain falls for 11.8 days and regularly aggregates up to 1.06" (27mm) of precipitation. In Snoqualmie Pass, Washington, during the entire year, the rain falls for 127.9 days and collects up to 28.58" (726mm) of precipitation.

Snowfall

January through June, September through December are months with snowfall in Snoqualmie Pass. September is the first month it typically snows in Snoqualmie Pass, Washington. Throughout September, in the average 0.8 snowfall days, it receives 0.24" (6mm) of snow. Throughout the year, there are 135.3 snowfall days, and 134.33" (3412mm) of snow is accumulated.

Daylight

In September, the average length of the day is 12h and 32min.
On the first day of September in Snoqualmie Pass, sunrise is at 6:25 am and sunset at 7:45 pm. On the last day of the month, sunrise is at 7:04 am and sunset at 6:46 pm PDT.

Sunshine

In Snoqualmie Pass, the average sunshine in September is 8.7h.

UV index

In Snoqualmie Pass, the average daily maximum UV index in September is 2. A UV Index reading of 2, and below, represents a low health risk from unsafe exposure to UV radiation for ordinary individuals.
Note: A typical high UV index of 2 in September suggests the following recommendations:
While extended sun exposure does not significantly affect most people, those with sensitive skin, children, and infants should always be protected. Limiting exposure to the direct Sun during midday hours can help prevent harmful UV radiation effects. Outfit yourself in sun-safe attire, like long sleeves, pants, a hat, and UV-blocking sunglasses. Mind you! Snow reflection can increase the intensity of the Sun's UV radiation nearly twofold.
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Frequently asked questions

What is the temperature in September in Snoqualmie Pass?

An average high-temperature, in September, in Snoqualmie Pass, is 62.1°F (16.7°C) and the average low-temperature is 41.2°F (5.1°C).

What is the average humidity in September in Snoqualmie Pass?

The average relative humidity in September is 75%.

How many days does it rain in September in Snoqualmie Pass?

In September, in Snoqualmie Pass, the rain falls for 11.8 days. Throughout September, 1.06" (27mm) of precipitation is accumulated.

When does it start to snow in Snoqualmie Pass?

September is the first month it typically snows in Snoqualmie Pass, Washington. Throughout September, in the average 0.8 snowfall days, it receives 0.24" (6mm) of snow.

What is the average length of the day in September in Snoqualmie Pass?

In September, the average day length in Snoqualmie Pass is 12h and 32min.

When are sunrise and sunset in September in Snoqualmie Pass?

In September, on the first day of the month, sunrise is at 6:25 am and sunset at 7:45 pm. On the last day of the month, in Snoqualmie Pass, Washington, sunrise is at 7:04 am and sunset at 6:46 pm PDT.

How many hours of sunshine does Snoqualmie Pass have in September?

The average sunshine duration in September in Snoqualmie Pass, Washington, is 8.7h.

How high is the UV index in September in Snoqualmie Pass?

In Snoqualmie Pass, Washington, the average daily maximum UV index in September is 2. A UV Index value of 2, and less, symbolizes a minimal hazard to health from exposure to Sun's UV rays.
Average humidity
Average rainfall days
Average snowfall days
Average daylight
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in September
Snoqualmie Pass, WA

Average temperature in September - Snoqualmie Pass, WA
  • Average high temperature in September: 62.1°F

The warmest month (with the highest average high temperature) is August (71.2°F).
The month with the lowest average high temperature is December (30.2°F).

  • Average low temperature in September: 41.2°F

The month with the highest average low temperature is August (45°F).
The coldest month (with the lowest average low temperature) is December (20.3°F).

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Average pressure in September
Snoqualmie Pass, WA

Average pressure in September - Snoqualmie Pass, WA
  • Average pressure in September: 29.99"Hg

The month with the highest atmospheric pressure is January (30.13"Hg).
The month with the lowest atmospheric pressure is August (29.97"Hg).

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Average wind speed in September
Snoqualmie Pass, WA

Average wind speed in September - Snoqualmie Pass, WA
  • Average wind speed in September: 3.9mph

The windiest month (with the highest average wind speed) is January (5mph).
The calmest month (with the lowest average wind speed) is September (3.9mph).

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Average humidity in September
Snoqualmie Pass, WA

Average humidity in September - Snoqualmie Pass, WA
  • Average humidity in September: 75%

The months with the highest relative humidity are January and February (93%).
The month with the lowest relative humidity is July (69%).

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Average rainfall in September
Snoqualmie Pass, WA

Average rainfall in September - Snoqualmie Pass, WA
  • Average rainfall in September: 1.06"

The wettest month (with the highest rainfall) is January (4.21").
The driest month (with the least rainfall) is July (0.51").

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Average rainfall days in September
Snoqualmie Pass, WA

Average rainfall days in September - Snoqualmie Pass, WA
  • Average rainfall days in September: 11.8 days

The month with the highest number of rainy days is May (15.7 days).
The month with the least rainy days is January (6.8 days).

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Average snowfall in September
Snoqualmie Pass, WA

Average snowfall in September - Snoqualmie Pass, WA
  • Average snowfall in September: 0.24"

The month with the highest snowfall is January (27.72").
The months with the least snowfall are July and August (0").

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Average snowfall days in September
Snoqualmie Pass, WA

Average snowfall days in September - Snoqualmie Pass, WA
  • Average snowfall days in September: 0.8 days

The month with the highest number of snowfall days is December (22.3 days).
The months with the least snowfall days are July and August (0 days).

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Average daylight in September /
Average sunshine in September
Snoqualmie Pass, WA

Average daylight in September / Average sunshine in September - Snoqualmie Pass, 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: 8h and 4min

The month with the most sunshine is August (Average sunshine: 10h and 54min).
The months with the least sunshine are January and February (Average sunshine: 3h and 0min).

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Average sunshine days in September
Snoqualmie Pass, WA

Average sunshine days in September - Snoqualmie Pass, WA
  • Average sunshine days in September: 15.1 days

The month with the most sunshine days is August (20.2 days).
The month with the least sunshine days is February (6 days).

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Average UV index in September
Snoqualmie Pass, WA

Average UV index in September - Snoqualmie Pass, WA
  • Average UV index in September: 2

The month with the highest UV index is July (UV index 5).
The months with the lowest UV index are January, February, November and December (UV index 1).

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Average cloud cover in September
Snoqualmie Pass, WA

Average cloud cover in September - Snoqualmie Pass, WA
  • Average cloud cover in September: 43

The month with the most cloud cover is February (Cloud cover 72).
The month with the least cloud cover is August (Cloud cover 30).

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Average visibility in September
Snoqualmie Pass, WA

Average visibility in September - Snoqualmie Pass, WA
  • Average visibility in September: 4mi

The months with the highest visibility are June, July and August (5mi).
The months with the lowest visibility are January, February, March and December (3mi).

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Snoqualmie Pass, Washington, USA

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