December weather forecast
Decatur, IL

Weather in December

The first month of the winter, December, is also a wintry month in Decatur, Illinois, with temperature in the range of an average low of 27.9°F (-2.3°C) and an average high of 38.5°F (3.6°C).

Temperature

In Decatur, Illinois, the average high-temperature drops, from a chilly 49.8°F (9.9°C) in November, to a cold 38.5°F (3.6°C). The average low-temperature, in December, is 27.9°F (-2.3°C).

Humidity

The average relative humidity in Decatur, Illinois, is 79%.

Rainfall

February and December are months with the least rain in Decatur when the rain falls for 7.1 days and typically aggregates up to 0.87" (22mm) of rain.

Snowfall

Months with snowfall in Decatur are January through April, November and December. In December, it is snowing for 5.3 days. Throughout December, 0.83" (21mm) of snow is accumulated. In Decatur, during the entire year, snow falls for 23.1 days, and aggregates up to 5.67" (144mm) of snow.

Daylight

With an average of 9.4h of daylight, December has the shortest days of the year.

Sunshine

In Decatur, the average sunshine is 4.6h.

UV index

January, February, November and December, with an average maximum UV index of 2, are months with the lowest UV index in Decatur. A UV Index value of 2, and less, symbolizes a low health risk from the exposure to the Sun's UV rays for average individuals.
Note: The daily maximum UV index of 2 interpret into the following advice:
For the majority, extended sun exposure is not of great concern. Infants and people with sensitive skin must always be protected. The Sun's most intense and consequently most harmful UV radiation during midday hours should be decreased by minimizing exposure and seeking shade. 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 December in Decatur?

In Decatur, Illinois, the average relative humidity in December is 79%.

What is the driest month in Decatur?

Months with the least rainfall in Decatur are February and December Rain falls for 7.1 days and accumulates 0.87" (22mm) of rain.

How much does it rain in Decatur in December?

In Decatur, Illinois, in December, during 7.1 rainfall days, 0.87" (22mm) of precipitation is typically accumulated.

How much does it snow in Decatur in December?

In December, it is snowing for 5.3 days. Throughout December, 0.83" (21mm) of snow is accumulated.

What is the month with the shortest days in Decatur?

December has the shortest days of the year in Decatur, Illinois, with an average of 9.4h of daylight.

How many hours of daylight does Decatur have in December?

In Decatur, the average length of the day in December is 9.4h.

How long on average sun shines in December in Decatur?

In December, the average sunshine is 4.6h.

When is the lowest UV index in Decatur?

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

How high is the UV index in December in Decatur?

The average daily maximum UV index in December in Decatur, Illinois, is 2. A UV Index value of 2, and less, symbolizes a low health risk from the exposure to the Sun's UV radiation.

Average temperature in December
Decatur, IL

Average temperature in December - Decatur, IL
  • Average high temperature in December: 38.5°F

The warmest month (with the highest average high temperature) is July (82°F).
The month with the lowest average high temperature is January (32.9°F).

  • Average low temperature in December: 27.9°F

The month with the highest average low temperature is July (65.7°F).
The coldest month (with the lowest average low temperature) is January (21.2°F).

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Average pressure in December
Decatur, IL

Average pressure in December - Decatur, IL
  • Average pressure in December: 30.12"

The month with the highest atmospheric pressure is January (30.15").
The month with the lowest atmospheric pressure is June (29.92").

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Average wind speed in December
Decatur, IL

Average wind speed in December - Decatur, IL
  • Average wind speed in December: 10.1mph

The windiest month (with the highest average wind speed) is January (10.7mph).
The calmest months (with the lowest average wind speed) are July and August (6.3mph).

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Average humidity in December
Decatur, IL

Average humidity in December - Decatur, IL
  • Average humidity in December: 79%

The month with the highest relative humidity is July (84%).
The month with the lowest relative humidity is October (70%).

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Average rainfall in December
Decatur, IL

Average rainfall in December - Decatur, IL
  • Average rainfall in December: 0.87"

The wettest month (with the highest rainfall) is May (2.01").
The driest months (with the least rainfall) are February and December (0.87").

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Average rainfall days in December
Decatur, IL

Average rainfall days in December - Decatur, IL
  • Average rainfall days in December: 7.1 days

The month with the highest number of rainy days is May (17 days).
The month with the least rainy days is February (5.8 days).

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Average snowfall in December
Decatur, IL

Average snowfall in December - Decatur, IL
  • Average snowfall in December: 0.83"

The month with the highest snowfall is January (1.85").
Months with the least snowfall are May, June, July, August, September and October (0").

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Average snowfall days in December
Decatur, IL

Average snowfall days in December - Decatur, IL
  • Average snowfall days in December: 5.3 days

The month with the highest number of snowfall days is January (7.2 days).
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
Decatur, IL

Average daylight in December / Average sunshine in December - Decatur, IL
  • Average daylight in December: 9.4h

The month with the longest days is June (Average daylight: 15h).
The month with the shortest days is December (Average daylight: 9.4h).

  • Average sunshine in December: 4.6h

The month with the most sunshine is June (Average sunshine: 10.4h).
The month with the least sunshine is January (Average sunshine: 4.1h).

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Average sunshine days in December
Decatur, IL

Average sunshine days in December - Decatur, IL
  • Average sunshine days in December: 19.4 days

The month with the most sunshine days is October (19.8 days).
The month with the least sunshine days is May (11.5 days).

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Average UV index in December
Decatur, IL

Average UV index in December - Decatur, IL
  • Average UV index in December: 2

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

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Average cloud cover in December
Decatur, IL

Average cloud cover in December - Decatur, IL
  • Average cloud cover in December: 52

The month with the most cloud cover is January (Cloud cover 56).
The month with the least cloud cover is September (Cloud cover 29).

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Average visibility in December
Decatur, IL

Average visibility in December - Decatur, IL
  • Average visibility in December: 6mi

Months with the highest visibility are January, February, March, April, May, June, September, October, November and December (6mi).
Months with the lowest visibility are July and August (5mi).

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