December weather forecast
O'Fallon, MO

Weather in December

The first month of the winter, December, is still a cold month in O'Fallon, Missouri, with an average temperature ranging between max 41.9°F (5.5°C) and min 30.4°F (-0.9°C).

Temperature

In O'Fallon, the average high-temperature in December decreases from a fresh 53.2°F (11.8°C) in November to a cold 41.9°F (5.5°C). In December, in O'Fallon, the average low-temperature is 30.4°F (-0.9°C).

Humidity

The average relative humidity in December is 76%.

Rainfall

December is the month with the least rainfall. Rain falls for 7 days and accumulates 0.91" (23mm) of precipitation.

Snowfall

Months with snowfall are January through March, November and December. In O'Fallon, in December, snow falls for 3.9 days, with typically accumulated 0.67" (17mm) of snow. Throughout the year, in O'Fallon, there are 19 snowfall days, and 4.13" (105mm) of snow is accumulated.

Daylight

The month with the shortest days is December, with an average of 9h and 30min of daylight.
On the first day of the month, sunrise is at 7:02 am and sunset at 4:41 pm. On the last day of December, sunrise is at 7:20 am and sunset at 4:50 pm CST.

Sunshine

The average sunshine in December is 4.8h.

UV index

January, February, November and December, with an average maximum UV index of 2, are months with the lowest UV index in O'Fallon, Missouri. A UV Index reading of 2, and below, represents a low threat to health from unsafe exposure to UV radiation for average individuals.
Note: The daily maximum UV index of 2 in December interpret into the following advice:
People with sensitive skin, children, and babies should always be protected from prolonged sun exposure. 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. 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 December in O'Fallon?

The average relative humidity in December in O'Fallon, Missouri, is 76%.

What is the driest month in O'Fallon?

The month with the least rainfall in O'Fallon is December, when the rain falls for 7 days and typically collects 0.91" (23mm) of precipitation.

How many days does it rain in December in O'Fallon?

In O'Fallon, Missouri, during December, the rain falls for 7 days and regularly aggregates up to 0.91" (23mm) of precipitation.

How many days does it snow in December in O'Fallon?

In O'Fallon, Missouri, during December, snow falls for 3.9 days and regularly aggregates up to 0.67" (17mm) of snow.

What is the month with the shortest days in O'Fallon?

The month with the shortest days is December, with an average of 9h and 30min of daylight.

How many hours of daylight does O'Fallon have in December?

In O'Fallon, Missouri, the average day length in December is 9h and 30min.

When are sunrise and sunset in December in O'Fallon?

In December, on the first day of the month, sunrise is at 7:02 am and sunset at 4:41 pm. On the last day of the month, in O'Fallon, sunrise is at 7:20 am and sunset at 4:50 pm CST.

How many hours of sunshine does O'Fallon have in December?

In O'Fallon, the average sunshine duration in December is 4.8h.

What is the month with the lowest UV index in O'Fallon?

The months with the lowest UV index in O'Fallon are January, February, November and December, with an average maximum UV index of 2.

What is the UV index reading in December in O'Fallon?

In O'Fallon, Missouri, the average daily maximum UV index in December is 2. A UV Index value of 2, and less, symbolizes a minimal health vulnerability from unprotected exposure to 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
O'Fallon, MO

Average temperature in December - O
  • Average high temperature in December: 41.9°F

The warmest month (with the highest average high temperature) is July (87.1°F).
The month with the lowest average high temperature is January (37.4°F).

  • Average low temperature in December: 30.4°F

The month with the highest average low temperature is July (68.5°F).
The coldest month (with the lowest average low temperature) is January (23.7°F).

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Average pressure in December
O'Fallon, MO

Average pressure in December - O
  • Average pressure in December: 30.13"Hg

The month with the highest atmospheric pressure is January (30.16"Hg).
The month with the lowest atmospheric pressure is June (29.92"Hg).

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Average wind speed in December
O'Fallon, MO

Average wind speed in December - O
  • Average wind speed in December: 8.6mph

The windiest month (with the highest average wind speed) is January (9.1mph).
The calmest month (with the lowest average wind speed) is July (5.5mph).

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Average humidity in December
O'Fallon, MO

Average humidity in December - O
  • Average humidity in December: 76%

The month with the highest relative humidity is May (79%).
The month with the lowest relative humidity is October (70%).

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Average rainfall in December
O'Fallon, MO

Average rainfall in December - O
  • Average rainfall in December: 0.91"

The wettest month (with the highest rainfall) is May (2.76").
The driest month (with the least rainfall) is December (0.91").

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Average rainfall days in December
O'Fallon, MO

Average rainfall days in December - O
  • Average rainfall days in December: 7 days

The month with the highest number of rainy days is May (15.7 days).
The month with the least rainy days is February (6.8 days).

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Average snowfall in December
O'Fallon, MO

Average snowfall in December - O
  • Average snowfall in December: 0.67"

The month with the highest snowfall is February (1.61").
The months with the least snowfall are April, May, June, July, August, September and October (0").

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Average snowfall days in December
O'Fallon, MO

Average snowfall days in December - O
  • Average snowfall days in December: 3.9 days

The months with the highest number of snowfall days are January and February (5.8 days).
The months with the least snowfall days are May, June, July, August, September and October (0 days).

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Average daylight in December /
Average sunshine in December
O'Fallon, MO

Average daylight in December / Average sunshine in December - O
  • Average daylight in December: 9h and 30min

The month with the longest days is June (Average daylight: 14h and 50min).
The month with the shortest days is December (Average daylight: 9h and 30min).

  • Average sunshine in December: 4h and 48min

The month with the most sunshine is June (Average sunshine: 10h and 30min).
The months with the least sunshine are January and February (Average sunshine: 4h and 42min).

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Average sunshine days in December
O'Fallon, MO

Average sunshine days in December - O
  • Average sunshine days in December: 20.6 days

The month with the most sunshine days is December (20.6 days).
The month with the least sunshine days is July (12.6 days).

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Average UV index in December
O'Fallon, MO

Average UV index in December - O
  • Average UV index in December: 2

The months with the highest UV index are May, June, July and August (UV index 6).
The months with the lowest UV index are January, February, November and December (UV index 2).

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Average cloud cover in December
O'Fallon, MO

Average cloud cover in December - O
  • Average cloud cover in December: 47

The month with the most cloud cover is January (Cloud cover 50).
The months with the least cloud cover are June, July, August and September (Cloud cover 28).

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Average visibility in December
O'Fallon, MO

Average visibility in December - O
  • 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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