December weather forecast
Roundup, MT

Weather in December

The first month of the winter, December, is still a freezing cold month in Roundup, Montana, with an average temperature ranging between max 31.1°F (-0.5°C) and min 18.5°F (-7.5°C).

Temperature

December is the coldest month, with an average high-temperature of 31.1°F (-0.5°C) and an average low-temperature of 18.5°F (-7.5°C).

Humidity

The average relative humidity in December in Roundup is 74%.

Rainfall

In December, the rain falls for 5.5 days. Throughout December, 0.59" (15mm) of precipitation is accumulated. In Roundup, 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. In Roundup, Montana, during December, snow falls for 9.6 days and regularly aggregates up to 2.72" (69mm) of snow. In Roundup, during the entire year, snow falls for 53.5 days and aggregates up to 18.58" (472mm) of snow.

Daylight

The month with the shortest days in Roundup is December, with an average of 8h and 40min of daylight.
On the first day of December in Roundup, sunrise is at 7:37 am and sunset at 4:29 pm. On the last day of the month, sunrise is at 7:57 am and sunset at 4:36 pm MST.

Sunshine

February and December, with an average of 5.2h of sunshine, are months with the least sunshine in Roundup.

UV index

With an average maximum UV index of 1, December is the month with the lowest UV index in Roundup. A UV Index of 2, and less, symbolizes a minimal health hazard from unprotected exposure to Sun's UV rays for the ordinary person.
Note: The average daily UV index of 1 in December transform into the following instructions:
Extended sun exposure is not an issue for the majority. Children, infants, and fair-skinned individuals always need to be protected. 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 coldest month in Roundup?

With an average high-temperature of 31.1°F (-0.5°C) and an average low-temperature of 18.5°F (-7.5°C), December is the coldest month in Roundup.

What is the average humidity in December in Roundup?

In Roundup, the average relative humidity in December is 74%.

How much does it rain in Roundup in December?

In Roundup, Montana, in December, it is raining for 5.5 days, with typically 0.59" (15mm) of accumulated precipitation.

How many days does it snow in December in Roundup?

In Roundup, in December, snow falls for 9.6 days, with typically accumulated 2.72" (69mm) of snow.

What is the month with the shortest days in Roundup?

December has the shortest days of the year in Roundup, with an average of 8h and 40min of daylight.

How many hours of daylight does Roundup have in December?

In Roundup, Montana, the average day length in December is 8h and 40min.

When is the sunrise / sunset in December in Roundup?

In December, on the first day of the month, sunrise is at 7:37 am and sunset at 4:29 pm. On the last day of the month, in Roundup, sunrise is at 7:57 am and sunset at 4:36 pm MST.

What is the month with the least sunshine in Roundup?

The months with the least sunshine in Roundup, Montana, are February and December, with an average of 5.2h of sunshine.

How many hours of sunshine does Roundup have in December?

In Roundup, Montana, the average sunshine duration in December is 5.2h.

What is the month with the lowest UV index in Roundup?

The month with the lowest UV index in Roundup, Montana, is December, with an average maximum UV index of 1.

What is the UV index reading in December in Roundup?

The average daily maximum UV index in December in Roundup, Montana, is 1. A UV Index estimate of 2, and below, represents a minimal hazard to health 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 December
Roundup, MT

Average temperature in December - Roundup, MT
  • Average high temperature in December: 31.1°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 December: 18.5°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 December
Roundup, MT

Average pressure in December - Roundup, MT
  • Average pressure in December: 30.12"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 December
Roundup, MT

Average wind speed in December - Roundup, MT
  • Average wind speed in December: 11mph

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 December
Roundup, MT

Average humidity in December - Roundup, MT
  • Average humidity in December: 74%

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 December
Roundup, MT

Average rainfall in December - Roundup, MT
  • Average rainfall in December: 0.59"

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 December
Roundup, MT

Average rainfall days in December - Roundup, MT
  • Average rainfall days in December: 5.5 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 December
Roundup, MT

Average snowfall in December - Roundup, MT
  • Average snowfall in December: 2.72"

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 December
Roundup, MT

Average snowfall days in December - Roundup, MT
  • Average snowfall days in December: 9.6 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 December /
Average sunshine in December
Roundup, MT

Average daylight in December / Average sunshine in December - Roundup, MT
  • Average daylight in December: 8h and 40min

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 December: 5h 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 December
Roundup, MT

Average sunshine days in December - Roundup, MT
  • Average sunshine days in December: 17.8 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 December
Roundup, MT

Average UV index in December - Roundup, MT
  • Average UV index in December: 1

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 December
Roundup, MT

Average cloud cover in December - Roundup, MT
  • Average cloud cover in December: 45

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 December
Roundup, MT

Average visibility in December - Roundup, MT
  • Average visibility in December: 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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