September weather forecast
Chelan, WA

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A small beachside condo over the deep blue sea, deep blue sky, and the deep blue hills afar, in Chelan, Washington
A small beachside condo over the deep blue sea, deep blue sky, and the deep blue hills afar, in Chelan, Washington

Weather in September

September marks the onset of autumn in Chelan, Washington, bringing a gradual drop in temperatures. This month’s weather dynamics indicate a soothing respite from summer’s heat, with an average high temperature dropping to 70.5°F (21.4°C). Compared to August, September brings a noticeable decrease in daylight hours, signifying shorter days. September also adds a slight increase in rainfall, rejuvenating the city’s greenery after a relatively dry summer. As October approaches, Chelan prepares for a marked drop in temperatures and increased rainfall.

Temperature

Transition from August to September is accompanied by a temperature drop, with average high-temperatures decreasing from a moderately hot 81.9°F (27.7°C) to a pleasant 70.5°F (21.4°C). An average low-temperature of 49.1°F (9.5°C) marks the nights throughout September.

Humidity

In September, the average relative humidity in Chelan is 52%.

Rainfall

In Chelan, in September, it is raining for 6.7 days, with typically 0.55" (14mm) of accumulated precipitation. In Chelan, during the entire year, the rain falls for 99.9 days and collects up to 10.47" (266mm) of precipitation.

Snowfall

January through April, September through December are months with snowfall in Chelan. September is the first month it typically snows. Throughout September, in the average 0.3 snowfall days, it receives 0.71" (18mm) of snow. Throughout the year, in Chelan, there are 48.7 snowfall days, and 28.62" (727mm) of snow is accumulated.

Daylight

In September, the average length of the day in Chelan is 12h and 33min.
On the first day of the month, sunrise is at 6:19 am and sunset at 7:40 pm. On the last day of September, in Chelan, Washington, sunrise is at 6:59 am and sunset at 6:40 pm PDT.

Sunshine

In September, the average sunshine in Chelan is 10.7h.

UV index

In Chelan, the average daily maximum UV index in September is 4. A UV Index of 3 to 5 symbolizes a moderate health risk from exposure to the Sun's UV rays for ordinary individuals.
Note: The maximum daily UV index, 4 in September, converts into the following recommendations:
Heed the precautions - Suggestions to avoid sunburn are made. Sun's radiation is most powerful around mid-day, so it's best to limit outdoor activities during this time. Wearing a wide-brim hat can block approximately 50% of UV radiation, protecting the eyes. Stay alert! Snow's reflective properties can almost double the UV radiation from the Sun.
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Frequently asked questions

What are the temperatures in Chelan in September?

During September, Chelan experiences an average high-temperature of 70.5°F (21.4°C) and a low-temperature of 49.1°F (9.5°C). The average heat index (a.k.a. 'feels like', 'real feel'), which factors the actual air temperature with the relative humidity, in August is estimated at 82.4°F (28°C).

What is the average humidity in September in Chelan?

The average relative humidity in September in Chelan is 52%.

How many days does it rain in September in Chelan?

In Chelan, in September, it is raining for 6.7 days, with typically 0.55" (14mm) of accumulated precipitation.

When does it start snowing in Chelan?

September is the first month it typically snows. Throughout September, in the average 0.3 snowfall days, it receives 0.71" (18mm) of snow.

How many hours of daylight does Chelan have in September?

The average day length in September in Chelan, Washington, is 12h and 33min.

When is the sunrise / sunset in September in Chelan?

On the first day of September in Chelan, Washington, sunrise is at 6:19 am and sunset at 7:40 pm. On the last day of the month, sunrise is at 6:59 am and sunset at 6:40 pm PDT.

How many hours of sunshine does Chelan have in September?

In Chelan, the average sunshine duration in September is 10.7h.

How high is the UV index in September in Chelan?

In Chelan, Washington, the average daily maximum UV index in September is 4. A UV Index reading of 3 to 5 represents a medium hazard to health from exposure to the Sun's UV radiation.
Average humidity
Average rainfall days
Average snowfall
Average snowfall days
Average daylight
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in September
Chelan, WA

Average temperature in September - Chelan, WA
  • Average high temperature in September: 70.5°F

The warmest month (with the highest average high temperature) is July (82.2°F).
The month with the lowest average high temperature is December (30.2°F).

  • Average low temperature in September: 49.1°F

The month with the highest average low temperature is August (55.8°F).
The coldest months (with the lowest average low temperature) are January and December (19°F).

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Average pressure in September
Chelan, WA

Average pressure in September - Chelan, WA
  • Average pressure in September: 29.97"Hg

The month with the highest atmospheric pressure is January (30.16"Hg).
The month with the lowest atmospheric pressure is August (29.93"Hg).

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Average wind speed in September
Chelan, WA

Average wind speed in September - Chelan, WA
  • Average wind speed in September: 5.3mph

The windiest month (with the highest average wind speed) is June (6.1mph).
The calmest months (with the lowest average wind speed) are January and December (3.5mph).

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Average humidity in September
Chelan, WA

Average humidity in September - Chelan, WA
  • Average humidity in September: 52%

The month with the highest relative humidity is January (90%).
The months with the lowest relative humidity are July and August (43%).

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Average rainfall in September
Chelan, WA

Average rainfall in September - Chelan, WA
  • Average rainfall in September: 0.55"

The wettest month (with the highest rainfall) is December (1.65").
The driest month (with the least rainfall) is July (0.16").

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Average rainfall days in September
Chelan, WA

Average rainfall days in September - Chelan, WA
  • Average rainfall days in September: 6.7 days

The month with the highest number of rainy days is March (12.8 days).
The month with the least rainy days is August (3.8 days).

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Average snowfall in September
Chelan, WA

Average snowfall in September - Chelan, WA
  • Average snowfall in September: 0.71"

The month with the highest snowfall is December (9.06").
The months with the least snowfall are May, June, July and August (0").

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Average snowfall days in September
Chelan, WA

Average snowfall days in September - Chelan, WA
  • Average snowfall days in September: 0.3 days

The month with the highest number of snowfall days is January (12 days).
The months with the least snowfall days are May, June, July and August (0 days).

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

Average daylight in September / Average sunshine in September - Chelan, WA
  • Average daylight in September: 12h and 4min

The month with the longest days is June (Average daylight: 16h and 0min).
The month with the shortest days is December (Average daylight: 8h and 30min).

  • Average sunshine in September: 10h and 4min

The months with the most sunshine are July and August (Average sunshine: 12h and 0min).
The month with the least sunshine is January (Average sunshine: 4h and 6min).

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Average sunshine days in September
Chelan, WA

Average sunshine days in September - Chelan, WA
  • Average sunshine days in September: 21.7 days

The month with the most sunshine days is July (25.7 days).
The month with the least sunshine days is March (13.2 days).

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Average UV index in September
Chelan, WA

Average UV index in September - Chelan, 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, March, October, November and December (UV index 2).

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Average cloud cover in September
Chelan, WA

Average cloud cover in September - Chelan, WA
  • Average cloud cover in September: 19

The month with the most cloud cover is January (Cloud cover 54).
The months with the least cloud cover are July and August (Cloud cover 12).

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Average visibility in September
Chelan, WA

Average visibility in September - Chelan, 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 and December (4mi).

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Chelan, Washington, USA

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