September weather forecast
Custer, SD

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Large, scenic rocks and trees around this tiny Sylvan Lake located in the tranquil Custer State Park in Custer City, South Dakota
Large, scenic rocks and trees around this tiny Sylvan Lake located in the tranquil Custer State Park in Custer City, South Dakota

Weather in September

September in Custer marks noticeable meteorological and aesthetic shifts, different from the warm August weather. The month ushers in autumn, and as warmth starts to give way, nature adorns a new color palette. A stark decrease in temperature and rainfall from August to September also aids the onset of the fall season. The city quickly transforms into a vibrant selection of fall colors under clear skies. Despite shorter daylight hours, September in Custer remains a fantastic time to experience the beauty of the transitioning season.

Temperature

As September arrives, Custer's weather displays a minor decrease in high-temperatures, transitioning from August's warm 80.1°F (26.7°C) to a pleasant 71.4°F (21.9°C). The temperature in Custer lowers to an average of 51.1°F (10.6°C) during September nights.

Humidity

The months with the lowest humidity in Custer are August and September, with an average relative humidity of 52%.

Rainfall

In September, the rain falls for 10 days. Throughout September, 1.22" (31mm) of precipitation is accumulated. In Custer, during the entire year, the rain falls for 135.4 days and collects up to 20.39" (518mm) of precipitation.

Snowfall

January through May, September through December are months with snowfall in Custer, South Dakota. September is the first month it typically snows in Custer, South Dakota. Throughout September, in the average 0.4 snowfall days, it receives 0.35" (9mm) of snow. Throughout the year, in Custer, there are 75.1 snowfall days, and 40.24" (1022mm) of snow is accumulated.

Daylight

In Custer, South Dakota, the average length of the day in September is 12h and 29min.
On the first day of the month, sunrise is at 6:18 am and sunset at 7:29 pm. On the last day of September, in Custer, South Dakota, sunrise is at 6:51 am and sunset at 6:36 pm MDT.

Sunshine

In Custer, the average sunshine in September is 10.5h.

UV index

In September, the average daily maximum UV index in Custer is 4. A UV Index reading of 3 to 5 represents a medium vulnerability from exposure to the Sun's UV rays for the average person.
Note: The maximum daily UV index, 4 in September, converts into the following recommendations:
Ensure safety - Imperative it is to shield skin and eyes from damage. The best time to avoid the Sun's harmful UV radiation is during midday when it's most potent. Sun-related eye harm can be minimized with proper sunglasses offering UVA and UVB coverage. Keep in mind! Snow's reflective quality can nearly double the intensity of the Sun's UV radiation.
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Frequently asked questions

What is the usual temperature for Custer in September?

In Custer, in September, the average high-temperature is 71.4°F (21.9°C), and the average low-temperature is 51.1°F (10.6°C). The average heat index (a.k.a. 'felt air temperature', 'apparent temperature'), which represents the influence of relative humidity on air temperature, in July is appraised at 82.4°F (28°C).

What is the least humid month in Custer?

The months with the lowest humidity in Custer, South Dakota, are August and September, with an average relative humidity of 52%.

What is the average humidity in September in Custer?

In September, the average relative humidity is 52%.

How much does it rain in Custer in September?

In Custer, South Dakota, during September, the rain falls for 10 days and regularly aggregates up to 1.22" (31mm) of precipitation.

When does it start snowing in Custer?

September is the first month it typically snows in Custer. Throughout September, in the average 0.4 snowfall days, it receives 0.35" (9mm) of snow.

How many hours of daylight does Custer have in September?

In Custer, South Dakota, the average day length in September is 12h and 29min.

When is the sunrise / sunset in September in Custer?

In September, on the first day of the month, sunrise is at 6:18 am and sunset at 7:29 pm. On the last day of the month, sunrise is at 6:51 am and sunset at 6:36 pm MDT.

How many hours of sunshine does Custer have in September?

In September, the average sunshine duration in Custer, South Dakota, is 10.5h.

How high is the UV index in September in Custer?

The average daily maximum UV index in September in Custer is 4. A UV Index reading of 3 to 5 represents a moderate vulnerability 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
Custer, SD

Average temperature in September - Custer, SD
  • Average high temperature in September: 71.4°F

The warmest month (with the highest average high temperature) is July (81.7°F).
The month with the lowest average high temperature is December (29.8°F).

  • Average low temperature in September: 51.1°F

The month with the highest average low temperature is July (60.4°F).
The coldest month (with the lowest average low temperature) is February (16.2°F).

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Average pressure in September
Custer, SD

Average pressure in September - Custer, SD
  • Average pressure in September: 29.93"Hg

The month with the highest atmospheric pressure is January (30.13"Hg).
The month with the lowest atmospheric pressure is June (29.84"Hg).

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Average wind speed in September
Custer, SD

Average wind speed in September - Custer, SD
  • Average wind speed in September: 8.1mph

The windiest month (with the highest average wind speed) is April (9.5mph).
The calmest month (with the lowest average wind speed) is August (7mph).

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Average humidity in September
Custer, SD

Average humidity in September - Custer, SD
  • Average humidity in September: 52%

The months with the highest relative humidity are January and February (77%).
The months with the lowest relative humidity are August and September (52%).

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Average rainfall in September
Custer, SD

Average rainfall in September - Custer, SD
  • Average rainfall in September: 1.22"

The wettest month (with the highest rainfall) is June (3.19").
The driest month (with the least rainfall) is January (0.47").

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Average rainfall days in September
Custer, SD

Average rainfall days in September - Custer, SD
  • Average rainfall days in September: 10 days

The month with the highest number of rainy days is May (18.6 days).
The month with the least rainy days is November (4.5 days).

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Average snowfall in September
Custer, SD

Average snowfall in September - Custer, SD
  • Average snowfall in September: 0.35"

The month with the highest snowfall is April (7.24").
The months with the least snowfall are June, July and August (0").

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Average snowfall days in September
Custer, SD

Average snowfall days in September - Custer, SD
  • Average snowfall days in September: 0.4 days

The month with the highest number of snowfall days is February (12.9 days).
The months with the least snowfall days are June, July and August (0 days).

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Average daylight in September /
Average sunshine in September
Custer, SD

Average daylight in September / Average sunshine in September - Custer, SD
  • Average daylight in September: 12h and 3min

The month with the longest days is June (Average daylight: 15h and 24min).
The month with the shortest days is December (Average daylight: 9h and 0min).

  • Average sunshine in September: 10h and 3min

The month with the most sunshine is August (Average sunshine: 11h and 42min).
The month with the least sunshine is February (Average sunshine: 6h and 0min).

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Average sunshine days in September
Custer, SD

Average sunshine days in September - Custer, SD
  • Average sunshine days in September: 17.3 days

The month with the most sunshine days is November (19.2 days).
The month with the least sunshine days is May (7.8 days).

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Average UV index in September
Custer, SD

Average UV index in September - Custer, SD
  • 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
Custer, SD

Average cloud cover in September - Custer, SD
  • Average cloud cover in September: 18

The month with the most cloud cover is April (Cloud cover 38).
The month with the least cloud cover is August (Cloud cover 17).

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Average visibility in September
Custer, SD

Average visibility in September - Custer, SD
  • Average visibility in September: 6mi

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

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Custer, South Dakota, USA

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