Contents
- Weather in December
- Frequently asked questions
- Average temperature in December
- Average pressure in December
- Average wind speed in December
- Average humidity in December
- Average rainfall in December
- Average rainfall days in December
- Average snowfall in December
- Average snowfall days in December
- Average daylight in December
- Average sunshine in December
- Average sunshine days in December
- Average UV index in December
- Average cloud cover in December
- Average visibility in December
Weather in December
Temperature
In Decatur, the beginning of December is marked by a lowered average high-temperature, shifting from November's frosty 49.8°F (9.9°C) to a wintry 38.5°F (3.6°C). The average low-temperature during December nights is a subzero cold 27.9°F (-2.3°C).Humidity
The average relative humidity in December is 79%.Rainfall
The months with the least rainfall are February and December Rain falls for 7.1 days and accumulates 0.87" (22mm) of rain.Snowfall
January through April, November and December are months with snowfall in Decatur. In Decatur, during December, snow falls for 5.3 days and regularly aggregates up to 0.83" (21mm) of snow. In Decatur, during the entire year, snow falls for 23.1 days and aggregates up to 5.67" (144mm) of snow.Daylight
December has the shortest days of the year, with an average of 9h and 24min of daylight.On the first day of the month, sunrise is at 6:58 am and sunset at 4:31 pm. On the last day of December, in Decatur, sunrise is at 7:17 am and sunset at 4:41 pm CST.
Sunshine
In Decatur, Illinois, the average sunshine in December 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. A UV Index reading of 2, and below, represents a minimal health hazard from unprotected exposure to Sun's UV rays for average individuals.Note: A maximum UV index of 2 in December translates into the following recommendations:
Extended exposure to the sun should always be avoided by children, infants, and those with sensitive skin. Being exposed to the midday Sun can have harmful effects due to strong UV radiation; always take precautions. Counter UV radiation's ill effects with clothing designed for sun safety and UV-resistant eyewear. Be aware! The reflective nature of snow can magnify the Sun's UV radiation almost twofold.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
How cold does it get in Decatur in December?
What is the average humidity in December in Decatur?
What is the driest month in Decatur?
How many days does it rain in December in Decatur?
How much does it snow in Decatur in December?
What is the month with the shortest days in Decatur?
How many hours of daylight does Decatur have in December?
When are sunrise and sunset in December in Decatur?
How long on average sun shines in December in Decatur?
What are the months with the lowest UV index in Decatur?
What is the UV index intensity in December in Decatur?
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).
Average pressure in December
Decatur, IL
- Average pressure in December: 30.12"Hg
The month with the highest atmospheric pressure is January (30.15"Hg).
The month with the lowest atmospheric pressure is June (29.92"Hg).
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).
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%).
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").
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).
Average snowfall in December
Decatur, IL
- Average snowfall in December: 0.83"
The month with the highest snowfall is January (1.85").
The months with the least snowfall are May, June, July, August, September and October (0").
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).
The months with the least snowfall days are May, June, July, August, September and October (0 days).
Average daylight in December /
Average sunshine in December
Decatur, IL
- Average daylight in December: 9h and 2min
The month with the longest days is June (Average daylight: 15h and 0min).
The month with the shortest days is December (Average daylight: 9h and 24min).
- Average sunshine in December: 4h and 4min
The month with the most sunshine is June (Average sunshine: 10h and 24min).
The month with the least sunshine is January (Average sunshine: 4h and 6min).
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).
Average UV index in December
Decatur, IL
- Average UV index in December: 2
The months with the highest UV index are June, July and August (UV index 6).
The months with the lowest UV index are January, February, November and December (UV index 2).
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).
Average visibility in December
Decatur, IL
- Average visibility in December: 6mi
The months with the highest visibility are January, February, March, April, May, June, September, October, November and December (6mi).
The months with the lowest visibility are July and August (5mi).
Decatur, Illinois, USA
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