December weather forecastMerna, IL
December
Weather in December
The first month of the winter, December, is still a cold month in Merna, Illinois, with an average temperature varying between 36.5°F (2.5°C) and 26.1°F (-3.3°C).Temperature
With the beginning of December, the average high-temperature shows a decrease, transitioning from a chilly 47.7°F (8.7°C) in November to a cold 36.5°F (2.5°C). Merna observes an average low-temperature of 26.1°F (-3.3°C) during December.Humidity
In December, the average relative humidity in Merna, Illinois, is 80%.Rainfall
The month with the least rainfall in Merna is December, when the rain falls for 9 days and typically collects 1.93" (49mm) of precipitation.Snowfall
Months with snowfall in Merna are January through April, October through December. In December, in Merna, it is snowing for 8.2 days. Throughout December, 2.64" (67mm) of snow is accumulated. In Merna, during the entire year, snow falls for 40.7 days and aggregates up to 17.01" (432mm) of snow.Daylight
With an average of 9h and 18min of daylight, December has the shortest days of the year in Merna.On the first day of December in Merna, sunrise is at 7:00 am and sunset at 4:29 pm. On the last day of the month, sunrise is at 7:18 am and sunset at 4:38 pm CST.
Sunshine
The average sunshine in December is 4.2h.UV index
The months with the lowest UV index in Merna are January, February, October through December, with an average maximum UV index of 2. A UV Index reading of 2, and below, represents a low health risk from unsafe exposure to UV radiation for average individuals.Note: The daily maximum UV index of 2 in December interprets into the following advice:
Babies, children, and those with sensitive skin should always avoid extended periods in the sun. Sun's radiation is most powerful around mid-day, so it's best to limit outdoor activities during this time. On days when the sun blazes, arm yourself with sunglasses that block UVA and UVB radiation. Stay alert! Snow's reflective properties can almost double the UV radiation from the Sun.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in December
Merna, IL
- Average high temperature in December: 36.5°F
The warmest month (with the highest average high temperature) is July (80.8°F).
The month with the lowest average high temperature is January (30.7°F).
- Average low temperature in December: 26.1°F
The month with the highest average low temperature is July (64.9°F).
The coldest month (with the lowest average low temperature) is January (18.9°F).
Average pressure in December
Merna, IL
- Average pressure in December: 30.11"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
Merna, IL
- Average wind speed in December: 10.6mph
The windiest month (with the highest average wind speed) is January (11.1mph).
The calmest month (with the lowest average wind speed) is August (6.6mph).
Average humidity in December
Merna, IL
- Average humidity in December: 80%
The month with the highest relative humidity is July (86%).
The month with the lowest relative humidity is October (71%).
Average rainfall in December
Merna, IL
- Average rainfall in December: 1.93"
The wettest month (with the highest rainfall) is May (4.57").
The driest month (with the least rainfall) is December (1.93").
Average rainfall days in December
Merna, IL
- Average rainfall days in December: 9 days
The month with the highest number of rainy days is May (20.1 days).
The month with the least rainy days is February (6.9 days).
Average snowfall in December
Merna, IL
- Average snowfall in December: 2.64"
The month with the highest snowfall is January (5.04").
The months with the least snowfall are May, June, July, August and September (0").
Average snowfall days in December
Merna, IL
- Average snowfall days in December: 8.2 days
The month with the highest number of snowfall days is January (12.8 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
Merna, IL
- Average daylight in December: 9h and 18min
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 18min).
- Average sunshine in December: 4h and 12min
The month with the most sunshine is June (Average sunshine: 9h and 48min).
The month with the least sunshine is January (Average sunshine: 3h and 42min).
Average sunshine days in December
Merna, IL
- Average sunshine days in December: 15 days
The month with the most sunshine days is November (17.4 days).
The month with the least sunshine days is May (8.4 days).
Average UV index in December
Merna, 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, October, November and December (UV index 2).
Average cloud cover in December
Merna, IL
- Average cloud cover in December: 56
The month with the most cloud cover is January (Cloud cover 60).
The months with the least cloud cover are August and September (Cloud cover 33).
Average visibility in December
Merna, IL
- Average visibility in December: 6mi
The months with the highest visibility are February, March, April, May, June, September, October, November and December (6mi).
The months with the lowest visibility are January, July and August (5mi).
