September weather forecast
Big Sky, MT

Vast fields and planted forests near the scenic mountainous region in Big Sky, Montana
Vast fields and planted forests near the scenic mountainous region in Big Sky, Montana

Weather in September

September, the first month of the autumn in Big Sky, is also an enjoyable month, with temperature in the range of an average high of 63.5°F (17.5°C) and an average low of 39.6°F (4.2°C).

Temperature

In Big Sky, the average high-temperature in September decreases from an agreeable 72.7°F (22.6°C) in August to an enjoyable 63.5°F (17.5°C). The average low-temperature, in September, is 39.6°F (4.2°C).

Humidity

In September, the average relative humidity is 57%.

Rainfall

In Big Sky, in September, during 11.1 rainfall days, 1.81" (46mm) of precipitation is typically accumulated. Throughout the year, there are 116.1 rainfall days, and 23.5" (597mm) of precipitation is accumulated.

Snowfall

Months with snowfall are January through December. In September, in Big Sky, it is snowing for 3.6 days. Throughout September, 5.04" (128mm) of snow is accumulated. In Big Sky, during the entire year, snow falls for 151.6 days and aggregates up to 124.06" (3151mm) of snow.

Daylight

In September, the average length of the day is 12h and 31min.
On the first day of September in Big Sky, sunrise is at 6:47 am and sunset at 8:02 pm. On the last day of the month, sunrise is at 7:22 am and sunset at 7:07 pm MDT.

Sunshine

The average sunshine in September in Big Sky is 9.8h.

UV index

The average daily maximum UV index in September is 3. A UV Index reading of 3 to 5 represents a medium vulnerability from exposure to the Sun's UV radiation for average individuals.
Note: In September, the average maximum UV index of 3 translate into the following recommendations:
Take precautions - Protection against skin and eye damage is obliged. The Sun's most intense and consequently most harmful UV radiation during midday hours should be decreased by minimizing exposure and seeking shade. On bright days sunglasses that block both UVA and UVB rays should be worn. A hat with a wide brim is extremely helpful, as it can prevent roughly 50% of UV radiation from reaching the eyes. Caution! The reflection of snow can nearly double the intensity of the Sun's UV radiation.
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FAQ

What is the temperature in September in Big Sky?

In Big Sky, in September, the average high-temperature is 63.5°F (17.5°C), and the average low-temperature is 39.6°F (4.2°C).

What is the average humidity in September in Big Sky?

In Big Sky, Montana, the average relative humidity in September is 57%.

How many days does it rain in September in Big Sky?

In Big Sky, Montana, in September, it is raining for 11.1 days, with typically 1.81" (46mm) of accumulated precipitation.

How much does it snow in Big Sky in September?

In September, in Big Sky, it is snowing for 3.6 days. Throughout September, 5.04" (128mm) of snow is accumulated.

How many hours of daylight does Big Sky have in September?

In September, the average day length is 12h and 31min.

What time are sunrise and sunset in September in Big Sky?

On the first day of September in Big Sky, Montana, sunrise is at 6:47 am and sunset at 8:02 pm. On the last day of the month, sunrise is at 7:22 am and sunset at 7:07 pm MDT.

How long on average sun shines in September in Big Sky?

The average sunshine duration in September is 9.8h.

What is the UV index intensity in September in Big Sky?

In September, the average daily maximum UV index in Big Sky, Montana, is 3. A UV Index estimate of 3 to 5 represents a medium health risk from unprotected exposure to UV radiation.
Average humidity
Average rainfall days
Average snowfall days
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in September
Big Sky, MT

Average temperature in September - Big Sky, MT
  • Average high temperature in September: 63.5°F

The warmest month (with the highest average high temperature) is July (74.8°F).
The month with the lowest average high temperature is December (22.5°F).

  • Average low temperature in September: 39.6°F

The month with the highest average low temperature is August (45.1°F).
The coldest month (with the lowest average low temperature) is December (7.9°F).

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Average pressure in September
Big Sky, MT

Average pressure in September - Big Sky, MT
  • Average pressure in September: 29.99"Hg

The month with the highest atmospheric pressure is January (30.22"Hg).
The month with the lowest atmospheric pressure is June (29.91"Hg).

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Average wind speed in September
Big Sky, MT

Average wind speed in September - Big Sky, MT
  • Average wind speed in September: 5.2mph

The windiest month (with the highest average wind speed) is January (7.1mph).
The calmest month (with the lowest average wind speed) is August (4.8mph).

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Average humidity in September
Big Sky, MT

Average humidity in September - Big Sky, MT
  • Average humidity in September: 57%

The months with the highest relative humidity are January and February (90%).
The month with the lowest relative humidity is August (51%).

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Average rainfall in September
Big Sky, MT

Average rainfall in September - Big Sky, MT
  • Average rainfall in September: 1.81"

The wettest months (with the highest rainfall) are April and May (2.91").
The driest month (with the least rainfall) is July (1.18").

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Average rainfall days in September
Big Sky, MT

Average rainfall days in September - Big Sky, MT
  • Average rainfall days in September: 11.1 days

The month with the highest number of rainy days is June (16.6 days).
The month with the least rainy days is February (4.3 days).

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Average snowfall in September
Big Sky, MT

Average snowfall in September - Big Sky, MT
  • Average snowfall in September: 5.04"

The month with the highest snowfall is April (19.88").
The month with the least snowfall is August (0.08").

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Average snowfall days in September
Big Sky, MT

Average snowfall days in September - Big Sky, MT
  • Average snowfall days in September: 3.6 days

The month with the highest number of snowfall days is March (21 days).
The month with the least snowfall days is August (0.3 days).

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Average daylight in September /
Average sunshine in September
Big Sky, MT

Average daylight in September / Average sunshine in September - Big Sky, MT
  • Average daylight in September: 12h and 31min

The month with the longest days is June (Average daylight: 15h and 35min).
The month with the shortest days is December (Average daylight: 8h and 49min).

  • Average sunshine in September: 9h and 48min

The month with the most sunshine is July (Average sunshine: 11h and 42min).
The month with the least sunshine is January (Average sunshine: 4h and 42min).

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Average sunshine days in September
Big Sky, MT

Average sunshine days in September - Big Sky, MT
  • Average sunshine days in September: 14.5 days

The month with the most sunshine days is September (14.5 days).
The month with the least sunshine days is May (5.7 days).

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Average UV index in September
Big Sky, MT

Average UV index in September - Big Sky, MT
  • Average UV index in September: 3

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

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Average cloud cover in September
Big Sky, MT

Average cloud cover in September - Big Sky, MT
  • Average cloud cover in September: 23

The month with the most cloud cover is February (Cloud cover 60).
The month with the least cloud cover is July (Cloud cover 17).

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Average visibility in September
Big Sky, MT

Average visibility in September - Big Sky, MT
  • Average visibility in September: 6mi

The months with the highest visibility are June, July, August, September and October (6mi).
The months with the lowest visibility are January, February, March, April and December (4mi).

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