September weather forecast
Halfmoon, MT

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Weather in September

September, the first month of the autumn in Halfmoon, is still a refreshing month, with an average temperature ranging between min 39.2°F (4°C) and max 65.5°F (18.6°C).

Temperature

Transition from August to September is accompanied by a temperature drop, with average high-temperatures decreasing from a moderately hot 76.8°F (24.9°C) to an enjoyable 65.5°F (18.6°C). Despite substantial daily fluctuations, the average low-temperature in Halfmoon, Montana, is a cold 39.2°F (4°C) during September.

Humidity

In September, the average relative humidity is 64%.

Rainfall

In September, the rain falls for 8.5 days. Throughout September, 0.71" (18mm) of precipitation is accumulated. Throughout the year, there are 126.4 rainfall days, and 11.22" (285mm) of precipitation is accumulated.

Snowfall

January through May, September through December are months with snowfall. September is the first month it typically snows. Throughout September, in the average 0.3 snowfall days, it receives 0.04" (1mm) of snow. Throughout the year, there are 97 snowfall days, and 33.86" (860mm) of snow is accumulated.

Daylight

In Halfmoon, the average length of the day in September is 12h and 34min.
On the first day of September, sunrise is at 6:55 am and sunset at 8:17 pm. On the last day of the month, sunrise is at 7:36 am and sunset at 7:17 pm MDT.

Sunshine

In September, the average sunshine in Halfmoon is 9.4h.

UV index

The average daily maximum UV index in September in Halfmoon is 3. A UV Index value of 3 to 5 symbolizes a medium vulnerability from unprotected exposure to Sun's UV rays for average individuals.
Note: In September, the maximum UV index of 3 suggests these recommendations:
Exercise prevention - Protecting skin and eyes from harm is required. The best time to avoid the Sun's harmful UV radiation is during midday when it's most potent. To cut down UV radiation exposure by about half, sport a wide-brim hat. Take heed! Reflection from the snow can almost amplify the Sun's UV radiation by double.
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Frequently asked questions

What are the temperatures in Halfmoon in September?

September temperatures vary between a high-temperature of 65.5°F (18.6°C) and a low-temperature of 39.2°F (4°C).

What is the average humidity in September in Halfmoon?

The average relative humidity in September in Halfmoon is 64%.

How much does it rain in Halfmoon in September?

In Halfmoon, Montana, during September, the rain falls for 8.5 days and regularly aggregates up to 0.71" (18mm) of precipitation.

When does it start snowing in Halfmoon?

September is the first month it typically snows in Halfmoon. Throughout September, in the average 0.3 snowfall days, it receives 0.04" (1mm) of snow.

How many hours of daylight does Halfmoon have in September?

The average day length in September in Halfmoon, Montana, is 12h and 34min.

When are sunrise and sunset in September in Halfmoon?

On the first day of September in Halfmoon, Montana, sunrise is at 6:55 am and sunset at 8:17 pm. On the last day of the month, sunrise is at 7:36 am and sunset at 7:17 pm MDT.

How many hours of sunshine does Halfmoon have in September?

The average sunshine duration in September in Halfmoon is 9.4h.

What is the UV index reading in September in Halfmoon?

In September, the average daily maximum UV index in Halfmoon, Montana, is 3. A UV Index value of 3 to 5 symbolizes a medium health risk from exposure to the Sun's UV radiation.
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
Halfmoon, MT

Average temperature in September - Halfmoon, MT
  • Average high temperature in September: 65.5°F

The warmest month (with the highest average high temperature) is July (77.9°F).
The month with the lowest average high temperature is December (25.7°F).

  • Average low temperature in September: 39.2°F

The month with the highest average low temperature is August (45.5°F).
The coldest month (with the lowest average low temperature) is February (13.5°F).

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Average pressure in September
Halfmoon, MT

Average pressure in September - Halfmoon, MT
  • 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 June (29.91"Hg).

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Average wind speed in September
Halfmoon, MT

Average wind speed in September - Halfmoon, MT
  • Average wind speed in September: 3.8mph

The windiest month (with the highest average wind speed) is April (4.6mph).
The calmest months (with the lowest average wind speed) are August and December (3.7mph).

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Average humidity in September
Halfmoon, MT

Average humidity in September - Halfmoon, MT
  • Average humidity in September: 64%

The month with the highest relative humidity is January (93%).
The month with the lowest relative humidity is August (55%).

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Average rainfall in September
Halfmoon, MT

Average rainfall in September - Halfmoon, MT
  • Average rainfall in September: 0.71"

The wettest month (with the highest rainfall) is June (1.42").
The driest month (with the least rainfall) is August (0.43").

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Average rainfall days in September
Halfmoon, MT

Average rainfall days in September - Halfmoon, MT
  • Average rainfall days in September: 8.5 days

The month with the highest number of rainy days is April (15.8 days).
The month with the least rainy days is August (6.3 days).

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Average snowfall in September
Halfmoon, MT

Average snowfall in September - Halfmoon, MT
  • Average snowfall in September: 0.04"

The month with the highest snowfall is January (7.72").
The months with the least snowfall are June, July and August (0").

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Average snowfall days in September
Halfmoon, MT

Average snowfall days in September - Halfmoon, MT
  • Average snowfall days in September: 0.3 days

The month with the highest number of snowfall days is December (19.1 days).
The months with the least snowfall days are July and August (0 days).

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Average daylight in September /
Average sunshine in September
Halfmoon, MT

Average daylight in September / Average sunshine in September - Halfmoon, MT
  • 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 24min).

  • Average sunshine in September: 9h and 2min

The month with the most sunshine is July (Average sunshine: 11h and 54min).
The month with the least sunshine is January (Average sunshine: 3h and 30min).

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Average sunshine days in September
Halfmoon, MT

Average sunshine days in September - Halfmoon, MT
  • Average sunshine days in September: 19 days

The month with the most sunshine days is July (21.5 days).
The month with the least sunshine days is March (7.7 days).

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Average UV index in September
Halfmoon, MT

Average UV index in September - Halfmoon, MT
  • Average UV index in September: 3

The month with the highest UV index is July (UV index 6).
The months with the lowest UV index are January, February, November and December (UV index 1).

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Average cloud cover in September
Halfmoon, MT

Average cloud cover in September - Halfmoon, MT
  • Average cloud cover in September: 24

The month with the most cloud cover is January (Cloud cover 65).
The months with the least cloud cover are July and August (Cloud cover 15).

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Average visibility in September
Halfmoon, MT

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

The months with the highest visibility are May, June, July, August, September and October (6mi).
The month with the lowest visibility is January (3mi).

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Halfmoon, Montana, USA

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