December weather forecastSullivan, IL
December
Weather in December
The first month of the winter, December, is also a wintry month in Sullivan, Illinois, with temperature in the range of an average low of 28.4°F (-2°C) and an average high of 38.8°F (3.8°C).Temperature
December's onset corresponds with a shift in the average high-temperature, moving from a chilly 49.8°F (9.9°C) in November to a wintry 38.8°F (3.8°C). In the month of December, Sullivan witnesses a consistent average low-temperature of 28.4°F (-2°C).Humidity
In December, the average relative humidity in Sullivan is 79%.Rainfall
In Sullivan, in December, it is raining for 7.5 days, with typically 0.87" (22mm) of accumulated precipitation. Throughout the year, there are 130.9 rainfall days, and 15.43" (392mm) of precipitation is accumulated.Snowfall
Months with snowfall in Sullivan are January through April, November and December. In Sullivan, in December, during 4.5 snowfall days, 0.91" (23mm) of snow is typically accumulated. Throughout the year, there are 21.5 snowfall days, and 4.53" (115mm) of snow is accumulated.Daylight
With an average of 9h and 24min of daylight, December has the shortest days of the year.On the first day of December in Sullivan, sunrise is at 6:56 am and sunset at 4:30 pm. On the last day of the month, sunrise is at 7:14 am and sunset at 4:40 pm CST.
Sunshine
In December, 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. A UV Index of 2, and less, symbolizes a low threat to health from unprotected exposure to Sun's UV rays for average individuals.Note: In December, an average UV index of 2 transforms into the following instructions:
For the majority, extended sun exposure is not of great concern. Infants and people with sensitive skin must always be protected. The Sun's harshest UV rays are around midday; it's wise to seek shade and limit time outdoors. For minimizing sun-related eye damage, always choose sunglasses with UVA and UVB coverage. Note this! The Sun's UV radiation can nearly be doubled by the reflection off snow.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in December
Sullivan, IL
- Average high temperature in December: 38.8°F
The warmest month (with the highest average high temperature) is July (82.2°F).
The month with the lowest average high temperature is January (33.6°F).
- Average low temperature in December: 28.4°F
The month with the highest average low temperature is July (65.8°F).
The coldest month (with the lowest average low temperature) is January (21.6°F).
Average pressure in December
Sullivan, IL
- Average pressure in December: 30.13"Hg
The month with the highest atmospheric pressure is January (30.15"Hg).
The month with the lowest atmospheric pressure is June (29.93"Hg).
Average wind speed in December
Sullivan, IL
- Average wind speed in December: 9.9mph
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
Sullivan, 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
Sullivan, IL
- Average rainfall in December: 0.87"
The wettest month (with the highest rainfall) is June (1.85").
The driest month (with the least rainfall) is February (0.71").
Average rainfall days in December
Sullivan, IL
- Average rainfall days in December: 7.5 days
The month with the highest number of rainy days is May (16.3 days).
The month with the least rainy days is February (5.9 days).
Average snowfall in December
Sullivan, IL
- Average snowfall in December: 0.91"
The month with the highest snowfall is January (1.54").
The months with the least snowfall are May, June, July, August, September and October (0").
Average snowfall days in December
Sullivan, IL
- Average snowfall days in December: 4.5 days
The month with the highest number of snowfall days is January (6.4 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
Sullivan, IL
- Average daylight in December: 9h and 24min
The month with the longest days is June (Average daylight: 14h and 54min).
The month with the shortest days is December (Average daylight: 9h and 24min).
- Average sunshine in December: 4h and 36min
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
Sullivan, IL
- Average sunshine days in December: 19.8 days
The month with the most sunshine days is October (20.5 days).
The month with the least sunshine days is May (12.3 days).
Average UV index in December
Sullivan, 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
Sullivan, IL
- Average cloud cover in December: 53
The month with the most cloud cover is January (Cloud cover 56).
The month with the least cloud cover is June (Cloud cover 30).
Average visibility in December
Sullivan, 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).
