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
Start of December brings a shift in the average high-temperature, falling from November's frosty 45.9°F (7.7°C) to a wintry 35.1°F (1.7°C). During the nights of December, River Forest records an average temperature of 26.6°F (-3°C), a minor drop from daytime peaks.Humidity
In December, the average relative humidity is 80%.Rainfall
The month with the least rainfall is December, when the rain falls for 8.2 days and typically collects 1.57" (40mm) of precipitation.Snowfall
Months with snowfall in River Forest are January through May, October through December. In December, it is snowing for 8.3 days. Throughout December, 2.52" (64mm) of snow is accumulated. Throughout the year, there are 40.3 snowfall days, and 16.81" (427mm) of snow is accumulated.Daylight
December has the shortest days of the year, with an average of 9h and 12min of daylight.On the first day of the month, sunrise is at 7:00 am and sunset at 4:21 pm. On the last day of December, sunrise is at 7:18 am and sunset at 4:30 pm CST.
Sunshine
The average sunshine in December is 4.1h.UV index
The months with the lowest UV index are January and December, with an average maximum UV index of 1. A UV Index estimate of 2, and below, represents a minimal health hazard from unprotected exposure to Sun's UV rays for the average person.Note: A maximum high UV index of 1 in December translates into the following recommendations:
While many people can endure lengthy sun exposure, it remains imperative to safeguard babies, children, and fair-skinned individuals. Direct exposure to the Sun during its peak hours around mid-day should be minimized for safety. Experience reduced UV exposure by about half when donning a wide-brim hat. Remember to consider! The UV radiation from the Sun can be intensified nearly twice by the reflection of snow.
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?
What is the driest month?
How much does it rain in December?
How much does it snow in December?
What is the month with the shortest days?
What is the average length of the day in December?
When are sunrise and sunset in December in River Forest?
How long on average sun shines in December?
What are the months with the lowest UV index?
How high is the UV index in December?
Average temperature in December
River Forest, IL
- Average high temperature in December: 35.1°F
The warmest month (with the highest average high temperature) is July (79.7°F).
The month with the lowest average high temperature is January (28.9°F).
- Average low temperature in December: 26.6°F
The month with the highest average low temperature is July (67.5°F).
The coldest month (with the lowest average low temperature) is January (19.4°F).
Average pressure in December
River Forest, IL
- Average pressure in December: 30.09"Hg
The month with the highest atmospheric pressure is January (30.11"Hg).
The month with the lowest atmospheric pressure is June (29.92"Hg).
Average wind speed in December
River Forest, IL
- Average wind speed in December: 10.4mph
The windiest month (with the highest average wind speed) is January (11.1mph).
The calmest months (with the lowest average wind speed) are July and August (7mph).
Average humidity in December
River Forest, IL
- Average humidity in December: 80%
The month with the highest relative humidity is January (82%).
The month with the lowest relative humidity is October (72%).
Average rainfall in December
River Forest, IL
- Average rainfall in December: 1.57"
The wettest month (with the highest rainfall) is May (4.49").
The driest month (with the least rainfall) is December (1.57").
Average rainfall days in December
River Forest, IL
- Average rainfall days in December: 8.2 days
The month with the highest number of rainy days is May (18.8 days).
The month with the least rainy days is February (5.1 days).
Average snowfall in December
River Forest, IL
- Average snowfall in December: 2.52"
The month with the highest snowfall is February (4.69").
The months with the least snowfall are June, July, August and September (0").
Average snowfall days in December
River Forest, IL
- Average snowfall days in December: 8.3 days
The month with the highest number of snowfall days is January (10.8 days).
The months with the least snowfall days are June, July, August and September (0 days).
Average daylight in December /
Average sunshine in December
River Forest, IL
- Average daylight in December: 9h and 1min
The month with the longest days is June (Average daylight: 15h and 12min).
The month with the shortest days is December (Average daylight: 9h and 12min).
- Average sunshine in December: 4h and 1min
The month with the most sunshine is August (Average sunshine: 10h and 36min).
The month with the least sunshine is January (Average sunshine: 3h and 42min).
Average sunshine days in December
River Forest, IL
- Average sunshine days in December: 16.7 days
The month with the most sunshine days is December (16.7 days).
The month with the least sunshine days is July (9.9 days).
Average UV index in December
River Forest, IL
- Average UV index in December: 1
The months with the highest UV index are June, July and August (UV index 6).
The months with the lowest UV index are January and December (UV index 1).
Average cloud cover in December
River Forest, IL
- Average cloud cover in December: 58
The month with the most cloud cover is January (Cloud cover 61).
The month with the least cloud cover is August (Cloud cover 27).
Average visibility in December
River Forest, IL
- 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).
River Forest, Illinois, USA
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