September weather forecast and climate
Acton, MT

Weather in September

The first month of the autumn, September, is still a pleasant month in Acton, Montana, with temperature in the range of an average high of 73.2°F (22.9°C) and an average low of 52.5°F (11.4°C).

Temperature

In September, the average high-temperature drops, from a warm 83.5°F (28.6°C) in August, to a pleasant 73.2°F (22.9°C). In Acton, the average low-temperature is 52.5°F (11.4°C).

Humidity

In September, the average relative humidity is 44%.

Rainfall

In September, in Acton, Montana, the rain falls for 6.8 days. Throughout September, 0.67" (17mm) of precipitation is accumulated. Throughout the year, in Acton, there are 120.5 rainfall days, and 13.54" (344mm) of precipitation is accumulated.

Snowfall

Months with snowfall are January through May, September through December. September is the first month it typically snows. Throughout September, in the average 0.2 snowfall days, it receives 0.12" (3mm) of snow. Throughout the year, there are 68.6 snowfall days, and 32.56" (827mm) of snow is accumulated.

Daylight

In September, the average length of the day in Acton is 12.5h.

Sunshine

The average sunshine in Acton is 10.3h.

UV index

In Acton, the average daily maximum UV index in September is 4. A UV Index reading of 3 to 5 represents a moderate threat to health from the exposure to the Sun's UV rays for the ordinary person.
Note: The daily maximum UV index of 4 interpret into the following advice:
Take precautions - Protection against sunburn is recommended. The solar radiation is most powerful near the mid-day, so the exposure to the direct Sun should be reduced accordingly. Sun-protective clothing, a long-sleeved shirt and pants, a wide-brimmed hat, and UVA and UVB-blocking sunglasses are particularly helpful in blocking UV radiation's harmful effects. 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 Acton?

In September, the average relative humidity in Acton, Montana, is 44%.

How much does it rain in Acton in September?

In Acton, during September, the rain falls for 6.8 days and regularly aggregates up to 0.67" (17mm) of precipitation.

When does it start snowing in Acton?

September is the first month it typically snows in Acton. Throughout September, in the average 0.2 snowfall days, it receives 0.12" (3mm) of snow.

How many hours of daylight does Acton have in September?

In September, the average length of the day in Acton is 12.5h.

How long on average sun shines in September in Acton?

The average sunshine in September in Acton is 10.3h.

How high is the UV index in September in Acton?

The average daily maximum UV index in September in Acton is 4. A UV Index value of 3 to 5 symbolizes a moderate vulnerability from the exposure to the Sun's UV rays.

Average temperature in September
Acton, MT

Average temperature in September - Acton, MT
  • Average high temperature in September: 73.2°F

The warmest month (with the highest average high temperature) is July (85.5°F).
The month with the lowest average high temperature is December (31.1°F).

  • Average low temperature in September: 52.5°F

Months with the highest average low temperature are July and August (60.6°F).
The coldest month (with the lowest average low temperature) is February (18.3°F).

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Average pressure in September
Acton, MT

Average pressure in September - Acton, MT
  • Average pressure in September: 29.95"

The month with the highest atmospheric pressure is January (30.14").
The month with the lowest atmospheric pressure is June (29.86").

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Average wind speed in September
Acton, MT

Average wind speed in September - Acton, MT
  • Average wind speed in September: 8.1mph

The windiest month (with the highest average wind speed) is January (9.9mph).
The calmest month (with the lowest average wind speed) is July (7.1mph).

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Average humidity in September
Acton, MT

Average humidity in September - Acton, MT
  • Average humidity in September: 44%

The month with the highest relative humidity is January (76%).
The month with the lowest relative humidity is August (40%).

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Average rainfall in September
Acton, MT

Average rainfall in September - Acton, MT
  • Average rainfall in September: 0.67"

The wettest month (with the highest rainfall) is May (2.24").
The driest month (with the least rainfall) is July (0.43").

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Average rainfall days in September
Acton, MT

Average rainfall days in September - Acton, MT
  • Average rainfall days in September: 6.8 days

The month with the highest number of rainy days is May (17.8 days).
The month with the least rainy days is January (5.6 days).

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Average snowfall in September
Acton, MT

Average snowfall in September - Acton, MT
  • Average snowfall in September: 0.12"

The month with the highest snowfall is February (6.61").
Months with the least snowfall are June, July and August (0").

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Average snowfall days in September
Acton, MT

Average snowfall days in September - Acton, MT
  • Average snowfall days in September: 0.2 days

The month with the highest number of snowfall days is February (14.3 days).
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
Acton, MT

Average daylight in September / Average sunshine in September - Acton, MT
  • Average daylight in September: 12.5h

The month with the longest days is June (Average daylight: 15.7h).
The month with the shortest days is December (Average daylight: 8.7h).

  • Average sunshine in September: 10.3h

The month with the most sunshine is July (Average sunshine: 11.9h).
The month with the least sunshine is February (Average sunshine: 5.3h).

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Average sunshine days in September
Acton, MT

Average sunshine days in September - Acton, MT
  • Average sunshine days in September: 21.1 days

The month with the most sunshine days is September (21.1 days).
The month with the least sunshine days is April (9.8 days).

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Average UV index in September
Acton, MT

Average UV index in September - Acton, MT
  • Average UV index in September: 4

The month with the highest UV index is July (UV index 7).
Months with the lowest UV index are January, February, March, November and December (UV index 2).

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Average cloud cover in September
Acton, MT

Average cloud cover in September - Acton, MT
  • Average cloud cover in September: 20

The month with the most cloud cover is February (Cloud cover 46).
The month with the least cloud cover is July (Cloud cover 14).

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Average visibility in September
Acton, MT

Average visibility in September - Acton, MT
  • Average visibility in September: 6mi

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

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