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 December, the average high-temperature decreases from a chilly 48.7°F (9.3°C) in November to a wintry 37.6°F (3.1°C). December nights observe an average temperature dip to a subzero cold 27.5°F (-2.5°C).Humidity
The average relative humidity in December is 80%.Rainfall
In Royal, in December, during 6.9 rainfall days, 0.71" (18mm) of precipitation is typically accumulated. In Royal, during the entire year, the rain falls for 121.5 days and collects up to 13.46" (342mm) of precipitation.Snowfall
Months with snowfall are January through April, November and December. In Royal, in December, snow falls for 6.1 days, with typically accumulated 0.83" (21mm) of snow. Throughout the year, there are 26.9 snowfall days, and 3.78" (96mm) 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 the month, sunrise is at 6:55 am and sunset at 4:26 pm. On the last day of December, sunrise is at 7:14 am and sunset at 4:36 pm CST.
Sunshine
In December, the average sunshine is 4.5h.UV index
The months with the lowest UV index in Royal are January, February, November and December, with an average maximum UV index of 2. A UV Index reading of 2, and below, represents a low threat to health from exposure to the Sun's UV radiation for the average person.Note: A daily maximum UV index of 2 in December translates into the following instructions:
While most people can stay under the sun for an hour without burning, children must always be guarded against sun exposure. Avoiding direct sunlight during midday hours helps reduce the risk from intense UV radiation. 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. Guard yourself! Snow reflection can almost double the UV radiation from the Sun.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
How cold is December?
What is the average humidity in December?
How much does it rain in December?
How many days does it snow in December in Royal?
What is the month with the shortest days?
How many hours of daylight does Royal have in December?
When are sunrise and sunset in December?
How many hours of sunshine does Royal have in December?
What is the month with the lowest UV index?
How high is the UV index in December?
Average temperature in December
Royal, IL
- Average high temperature in December: 37.6°F
The warmest month (with the highest average high temperature) is July (81°F).
The month with the lowest average high temperature is January (31.5°F).
- Average low temperature in December: 27.5°F
The month with the highest average low temperature is July (64.8°F).
The coldest month (with the lowest average low temperature) is January (19.8°F).
Average pressure in December
Royal, IL
- Average pressure in December: 30.12"Hg
The month with the highest atmospheric pressure is January (30.14"Hg).
The month with the lowest atmospheric pressure is June (29.92"Hg).
Average wind speed in December
Royal, IL
- Average wind speed in December: 10.1mph
The windiest month (with the highest average wind speed) is January (10.7mph).
The calmest month (with the lowest average wind speed) is August (6.4mph).
Average humidity in December
Royal, IL
- Average humidity in December: 80%
The month with the highest relative humidity is July (85%).
The month with the lowest relative humidity is October (71%).
Average rainfall in December
Royal, IL
- Average rainfall in December: 0.71"
The wettest month (with the highest rainfall) is May (1.77").
The driest month (with the least rainfall) is February (0.67").
Average rainfall days in December
Royal, IL
- Average rainfall days in December: 6.9 days
The month with the highest number of rainy days is May (14.8 days).
The month with the least rainy days is February (4.6 days).
Average snowfall in December
Royal, IL
- Average snowfall in December: 0.83"
The month with the highest snowfall is February (1.38").
The months with the least snowfall are May, June, July, August, September and October (0").
Average snowfall days in December
Royal, IL
- Average snowfall days in December: 6.1 days
The month with the highest number of snowfall days is January (7.9 days).
The months with the least snowfall days are May, June, July, August and September (0 days).
Average daylight in December /
Average sunshine in December
Royal, 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 3min
The month with the most sunshine is June (Average sunshine: 10h and 6min).
The month with the least sunshine is January (Average sunshine: 4h and 0min).
Average sunshine days in December
Royal, IL
- Average sunshine days in December: 19.4 days
The month with the most sunshine days is November (20.4 days).
The month with the least sunshine days is July (11.3 days).
Average UV index in December
Royal, 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
Royal, IL
- Average cloud cover in December: 54
The month with the most cloud cover is January (Cloud cover 58).
The month with the least cloud cover is August (Cloud cover 31).
Average visibility in December
Royal, 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).
Royal, Illinois, USA
Weather forecast for your location
2. Allow the app to use your location