September weather forecast
West Yellowstone, MT

Weather in September

September, the first month of the autumn in West Yellowstone, is still a comfortable month, with an average temperature ranging between max 61.9°F (16.6°C) and min 37.6°F (3.1°C).

Temperature

In September, the average high-temperature decreases from an agreeable 71.4°F (21.9°C) in August to an enjoyable 61.9°F (16.6°C). The average low-temperature, in West Yellowstone, is 37.6°F (3.1°C).

Humidity

In West Yellowstone, the average relative humidity in September is 57%.

Rainfall

In West Yellowstone, during September, the rain falls for 10.5 days and regularly aggregates up to 1.57" (40mm) of precipitation. In West Yellowstone, during the entire year, the rain falls for 109.2 days and collects up to 23.15" (588mm) of precipitation.

Snowfall

Months with snowfall are January through July, September through December. September is the first month it typically snows in West Yellowstone. Throughout September, in the average 2.4 snowfall days, it receives 3.27" (83mm) of snow. In West Yellowstone, during the entire year, snow falls for 159.3 days and aggregates up to 120.47" (3060mm) of snow.

Daylight

In West Yellowstone, the average length of the day in September is 12h and 30min.
On the first day of the month, sunrise is at 6:47 am and sunset at 8:01 pm. On the last day of September, sunrise is at 7:21 am and sunset at 7:07 pm MDT.

Sunshine

In West Yellowstone, the average sunshine in September is 9.8h.

UV index

In West Yellowstone, the average daily maximum UV index in September is 2. A UV Index reading of 2, and below, represents a minimal health hazard from unprotected exposure to Sun's UV rays for average individuals.
Note: In September, the average maximum UV index of 2 translate into the following recommendations:
For the majority, extended sun exposure is not of great concern. Infants and people with sensitive skin must always be protected. The Sun's most intense and consequently most harmful UV radiation during midday hours should be decreased by minimizing exposure and seeking shade. 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. Caution! The reflection of snow can nearly double the intensity of the Sun's UV radiation.
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FAQ

What is the average humidity in September in West Yellowstone?

In September, the average relative humidity in West Yellowstone is 57%.

How much does it rain in West Yellowstone in September?

In September, in West Yellowstone, Montana, the rain falls for 10.5 days. Throughout September, 1.57" (40mm) of precipitation is accumulated.

When does it start snowing in West Yellowstone?

September is the first month it typically snows in West Yellowstone, Montana. Throughout September, in the average 2.4 snowfall days, it receives 3.27" (83mm) of snow.

How many hours of daylight does West Yellowstone have in September?

In West Yellowstone, the average day length in September is 12h and 30min.

What time are sunrise and sunset in September in West Yellowstone?

On the first day of September in West Yellowstone, Montana, sunrise is at 6:47 am and sunset at 8:01 pm. On the last day of the month, sunrise is at 7:21 am and sunset at 7:07 pm MDT.

How many hours of sunshine does West Yellowstone have in September?

In September, the average sunshine duration in West Yellowstone, Montana, is 9.8h.

How high is the UV index in September in West Yellowstone?

In September, the average daily maximum UV index in West Yellowstone is 2. A UV Index estimate of 2, and below, represents a minimal health vulnerability from exposure to the Sun's 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
West Yellowstone, MT

Average temperature in September - West Yellowstone, MT
  • Average high temperature in September: 61.9°F

The warmest month (with the highest average high temperature) is July (72.9°F).
The month with the lowest average high temperature is December (20.1°F).

  • Average low temperature in September: 37.6°F

The month with the highest average low temperature is August (43.7°F).
The coldest month (with the lowest average low temperature) is December (4.8°F).

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Average pressure in September
West Yellowstone, MT

Average pressure in September - West Yellowstone, MT
  • Average pressure in September: 29.99"Hg

The month with the highest atmospheric pressure is January (30.24"Hg).
The month with the lowest atmospheric pressure is June (29.92"Hg).

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Average wind speed in September
West Yellowstone, MT

Average wind speed in September - West Yellowstone, MT
  • Average wind speed in September: 6mph

The windiest month (with the highest average wind speed) is June (6.8mph).
The calmest month (with the lowest average wind speed) is August (5.8mph).

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Average humidity in September
West Yellowstone, MT

Average humidity in September - West Yellowstone, MT
  • Average humidity in September: 57%

The month with the highest relative humidity is February (95%).
The month with the lowest relative humidity is August (50%).

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Average rainfall in September
West Yellowstone, MT

Average rainfall in September - West Yellowstone, MT
  • Average rainfall in September: 1.57"

The wettest month (with the highest rainfall) is May (2.8").
The driest month (with the least rainfall) is July (0.91").

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Average rainfall days in September
West Yellowstone, MT

Average rainfall days in September - West Yellowstone, MT
  • Average rainfall days in September: 10.5 days

The month with the highest number of rainy days is May (17.4 days).
The month with the least rainy days is January (2.2 days).

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Average snowfall in September
West Yellowstone, MT

Average snowfall in September - West Yellowstone, MT
  • Average snowfall in September: 3.27"

The month with the highest snowfall is February (17.83").
The month with the least snowfall is August (0").

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Average snowfall days in September
West Yellowstone, MT

Average snowfall days in September - West Yellowstone, MT
  • Average snowfall days in September: 2.4 days

The month with the highest number of snowfall days is March (24.4 days).
The months with the least snowfall days are July and August (0.2 days).

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Average daylight in September /
Average sunshine in September
West Yellowstone, MT

Average daylight in September / Average sunshine in September - West Yellowstone, MT
  • Average daylight in September: 12h and 30min

The month with the longest days is June (Average daylight: 15h and 31min).
The month with the shortest days is December (Average daylight: 8h and 53min).

  • Average sunshine in September: 9h and 48min

The month with the most sunshine is July (Average sunshine: 11h and 48min).
The months with the least sunshine are January, February and December (Average sunshine: 3h and 18min).

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Average sunshine days in September
West Yellowstone, MT

Average sunshine days in September - West Yellowstone, MT
  • Average sunshine days in September: 14.7 days

The months with the most sunshine days are July and September (14.7 days).
The month with the least sunshine days is February (5.3 days).

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Average UV index in September
West Yellowstone, MT

Average UV index in September - West Yellowstone, MT
  • 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, March, April, October, November and December (UV index 1).

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Average cloud cover in September
West Yellowstone, MT

Average cloud cover in September - West Yellowstone, MT
  • Average cloud cover in September: 22

The month with the most cloud cover is February (Cloud cover 76).
The month with the least cloud cover is July (Cloud cover 16).

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Average visibility in September
West Yellowstone, MT

Average visibility in September - West Yellowstone, MT
  • Average visibility in September: 6mi

The months with the highest visibility are June, July, August and September (6mi).
The months with the lowest visibility are January, February, March and December (3mi).

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