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
As November transitions to December, the average high-temperature falls from a chilly 45.9°F (7.7°C) to an icy 32°F (0°C). Throughout December, an average low-temperature of 21°F (-6.1°C) is experienced.Humidity
The average relative humidity in December is 80%.Rainfall
In December, the rain falls for 4.8 days. Throughout December, 1.34" (34mm) of precipitation is accumulated. In Herndon, during the entire year, the rain falls for 125.7 days and collects up to 26.5" (673mm) of precipitation.Snowfall
January through May, October through December are months with snowfall. In Herndon, during December, snow falls for 8.3 days and regularly aggregates up to 2.64" (67mm) of snow. In Herndon, during the entire year, snow falls for 38.1 days and aggregates up to 15.31" (389mm) of snow.Daylight
With an average of 9h and 12min of daylight, December has the shortest days of the year.On the first day of December, sunrise is at 7:26 am and sunset at 4:47 pm. On the last day of the month, sunrise is at 7:44 am and sunset at 4:56 pm CST.
Sunshine
In December, the average sunshine is 4.7h.UV index
The months with the lowest UV index are January, February, October through December, with an average maximum UV index of 2. A UV Index value of 2, and less, symbolizes a minimal health vulnerability from exposure to the Sun's UV radiation for ordinary individuals.Note: An average UV index of 2 in December transforms into this advice:
Long-term sun exposure is typically not a concern for most. However, those with sensitive skin, infants, and children must always have protection. The best time to avoid the Sun's harmful UV radiation is during midday when it's most potent. Select sunglasses that boast both UVA and UVB protection to limit the adverse effects of the sun on the eyes. Consider carefully! The reflective quality of snow can almost double the intensity of the Sun's UV radiation.
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?
What is the month with the shortest days?
How many hours of daylight does Herndon have in December?
When is the sunrise / sunset in December?
How long on average sun shines in December?
What are the months with the lowest UV index?
What is the UV index intensity in December?
Average temperature in December
Herndon, IA
- Average high temperature in December: 32°F
The warmest month (with the highest average high temperature) is July (82°F).
The month with the lowest average high temperature is January (26.8°F).
- Average low temperature in December: 21°F
The month with the highest average low temperature is July (64.6°F).
The coldest month (with the lowest average low temperature) is January (13.5°F).
Average pressure in December
Herndon, IA
- Average pressure in December: 30.12"Hg
The month with the highest atmospheric pressure is January (30.16"Hg).
The month with the lowest atmospheric pressure is June (29.88"Hg).
Average wind speed in December
Herndon, IA
- Average wind speed in December: 10.2mph
The windiest month (with the highest average wind speed) is April (10.7mph).
The calmest months (with the lowest average wind speed) are July and August (7.1mph).
Average humidity in December
Herndon, IA
- Average humidity in December: 80%
The month with the highest relative humidity is January (84%).
The month with the lowest relative humidity is October (69%).
Average rainfall in December
Herndon, IA
- Average rainfall in December: 1.34"
The wettest month (with the highest rainfall) is May (4.06").
The driest month (with the least rainfall) is January (0.87").
Average rainfall days in December
Herndon, IA
- Average rainfall days in December: 4.8 days
The month with the highest number of rainy days is June (17.3 days).
The month with the least rainy days is February (3.4 days).
Average snowfall in December
Herndon, IA
- Average snowfall in December: 2.64"
The month with the highest snowfall is January (4.29").
The months with the least snowfall are June, July, August and September (0").
Average snowfall days in December
Herndon, IA
- Average snowfall days in December: 8.3 days
The month with the highest number of snowfall days is January (9.8 days).
The months with the least snowfall days are June, July, August and September (0 days).
Average daylight in December /
Average sunshine in December
Herndon, IA
- 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 4min
The month with the most sunshine is July (Average sunshine: 10h and 12min).
The month with the least sunshine is January (Average sunshine: 4h and 12min).
Average sunshine days in December
Herndon, IA
- Average sunshine days in December: 18.8 days
The month with the most sunshine days is November (19.4 days).
The month with the least sunshine days is June (11.1 days).
Average UV index in December
Herndon, IA
- Average UV index in December: 2
The months with the highest UV index are June and July (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
Herndon, IA
- Average cloud cover in December: 50
The month with the most cloud cover is January (Cloud cover 55).
The months with the least cloud cover are July and September (Cloud cover 30).
Average visibility in December
Herndon, IA
- 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).
Herndon, Iowa, USA
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