September weather forecast
Roundup, MT

Weather in September

The first month of the autumn, September, is also an agreeable month in Roundup, Montana, with an average temperature ranging between min 53.2°F (11.8°C) and max 72.7°F (22.6°C).

Temperature

In September, the average high-temperature decreases from a warm 82.8°F (28.2°C) in August to a pleasant 72.7°F (22.6°C). In Roundup, the average low-temperature is 53.2°F (11.8°C).

Humidity

The average relative humidity in September in Roundup is 44%.

Rainfall

In Roundup, during September, the rain falls for 8 days and regularly aggregates up to 0.94" (24mm) of precipitation. In Roundup, Montana, during the entire year, the rain falls for 114.3 days and collects up to 12.13" (308mm) of precipitation.

Snowfall

January through May, September through December are months with snowfall. September is the first month it typically snows in Roundup, Montana. Throughout September, in the average 0.3 snowfall days, it receives 0.12" (3mm) of snow. Throughout the year, in Roundup, there are 53.5 snowfall days, and 18.58" (472mm) of snow is accumulated.

Daylight

In Roundup, the average length of the day in September is 12h and 32min.
On the first day of September, sunrise is at 6:34 am and sunset at 7:53 pm. On the last day of the month, sunrise is at 7:11 am and sunset at 6:56 pm MDT.

Sunshine

The average sunshine in September is 10.2h.

UV index

In Roundup, the average daily maximum UV index in September is 4. A UV Index of 3 to 5 symbolizes a moderate threat to health from exposure to the Sun's UV rays for ordinary individuals.
Note: The average daily UV index of 4 in September transform into the following instructions:
Take precautions - Protection against sun damage is advised. The solar radiation is most powerful near the mid-day, so the exposure to the direct Sun should be reduced accordingly. 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. Beware! The strength of the UV rays is increased nearly double-fold by the reflection of the snow.
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FAQ

What is the average humidity in September in Roundup?

The average relative humidity in September in Roundup, Montana, is 44%.

How much does it rain in Roundup in September?

In Roundup, during September, the rain falls for 8 days and regularly aggregates up to 0.94" (24mm) of precipitation.

When does it start to snow in Roundup?

September is the first month it typically snows in Roundup. Throughout September, in the average 0.3 snowfall days, it receives 0.12" (3mm) of snow.

How many hours of daylight does Roundup have in September?

In Roundup, Montana, the average day length in September is 12h and 32min.

When are sunrise and sunset in September in Roundup?

On the first day of September, sunrise is at 6:34 am and sunset at 7:53 pm. On the last day of the month, sunrise is at 7:11 am and sunset at 6:56 pm MDT.

How many hours of sunshine does Roundup have in September?

In September, the average sunshine duration is 10.2h.

What is the UV index reading in September in Roundup?

In September, the average daily maximum UV index in Roundup is 4. A UV Index estimate of 3 to 5 represents a medium hazard to health 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
Roundup, MT

Average temperature in September - Roundup, MT
  • Average high temperature in September: 72.7°F

The warmest month (with the highest average high temperature) is July (84.7°F).
The month with the lowest average high temperature is December (31.1°F).

  • Average low temperature in September: 53.2°F

The month with the highest average low temperature is July (62.4°F).
The coldest month (with the lowest average low temperature) is February (18°F).

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Average pressure in September
Roundup, MT

Average pressure in September - Roundup, MT
  • 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 (29.85"Hg).

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Average wind speed in September
Roundup, MT

Average wind speed in September - Roundup, MT
  • Average wind speed in September: 9.3mph

The windiest month (with the highest average wind speed) is January (11.2mph).
The calmest months (with the lowest average wind speed) are July and August (8.5mph).

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Average humidity in September
Roundup, MT

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

The month with the highest relative humidity is January (77%).
The month with the lowest relative humidity is August (39%).

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Average rainfall in September
Roundup, MT

Average rainfall in September - Roundup, MT
  • Average rainfall in September: 0.94"

The wettest month (with the highest rainfall) is May (1.97").
The driest month (with the least rainfall) is January (0.55").

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Average rainfall days in September
Roundup, MT

Average rainfall days in September - Roundup, MT
  • Average rainfall days in September: 8 days

The month with the highest number of rainy days is May (15.6 days).
The month with the least rainy days is February (4.6 days).

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Average snowfall in September
Roundup, MT

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

The month with the highest snowfall is February (3.78").
The months with the least snowfall are June, July and August (0").

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Average snowfall days in September
Roundup, MT

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

The month with the highest number of snowfall days is February (11.1 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
Roundup, MT

Average daylight in September / Average sunshine in September - Roundup, MT
  • Average daylight in September: 12h and 32min

The month with the longest days is June (Average daylight: 15h and 45min).
The month with the shortest days is December (Average daylight: 8h and 40min).

  • Average sunshine in September: 10h and 12min

The month with the most sunshine is July (Average sunshine: 11h and 48min).
The months with the least sunshine are February and December (Average sunshine: 5h and 12min).

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Average sunshine days in September
Roundup, MT

Average sunshine days in September - Roundup, MT
  • Average sunshine days in September: 19.5 days

The month with the most sunshine days is September (19.5 days).
The month with the least sunshine days is April (12.8 days).

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Average UV index in September
Roundup, MT

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

The month with the highest UV index is July (UV index 7).
The month with the lowest UV index is December (UV index 1).

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Average cloud cover in September
Roundup, MT

Average cloud cover in September - Roundup, MT
  • Average cloud cover in September: 22

The month with the most cloud cover is February (Cloud cover 47).
The months with the least cloud cover are July and August (Cloud cover 16).

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Average visibility in September
Roundup, MT

Average visibility in September - Roundup, MT
  • 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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