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
With the beginning of December, the average high-temperature shows a small decrease, transitioning from a fresh 53.6°F (12°C) in November to a frosty 45.1°F (7.3°C). The average low-temperature, in December, is a cold 32°F (0°C).Humidity
December is the most humid month, with an average relative humidity of 78%.Rainfall
In December, the rain falls for 10.5 days. Throughout December, 2.68" (68mm) of precipitation is accumulated. Throughout the year, there are 158.1 rainfall days, and 31.46" (799mm) of precipitation is accumulated.Snowfall
January through April, November and December are months with snowfall. In December, it is snowing for 2.7 days. Throughout December, 1.97" (50mm) of snow is accumulated. In Herndon, during the entire year, snow falls for 16.7 days and aggregates up to 12.28" (312mm) of snow.Daylight
The month with the shortest days is December, with an average of 9h and 30min of daylight.On the first day of December, sunrise is at 7:09 am and sunset at 4:47 pm. On the last day of the month, sunrise is at 7:28 am and sunset at 4:57 pm EST.
Sunshine
January, February and December, with an average of 5h of sunshine, are months with the least sunshine in Herndon.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 reading of 2, and below, represents a low health risk from unprotected exposure to Sun's UV rays for the ordinary person.Note: The UV index of 2 during December leads to these advisories:
Children must always have sun protection, unlike most people, who can tolerate up to an hour in the sun without any burns. The Sun is at its harshest during midday; protect yourself by staying in shaded areas and minimizing exposure. Sun protection is enhanced with clothing that boasts a tight weave yet offers a loose fit. 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
What is the average December temperature?
What is the most humid month?
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?
What time are sunrise and sunset in December in Herndon?
What are the months with the least sunshine?
How long on average sun shines in December?
What is the month with the lowest UV index?
What is the UV index reading in December in Herndon?
Average temperature in December
Herndon, VA
- Average high temperature in December: 45.1°F
The warmest month (with the highest average high temperature) is July (87.8°F).
The month with the lowest average high temperature is January (39.7°F).
- Average low temperature in December: 32°F
The month with the highest average low temperature is July (67.3°F).
The coldest month (with the lowest average low temperature) is January (25.9°F).
Average pressure in December
Herndon, VA
- Average pressure in December: 30.11"Hg
The month with the highest atmospheric pressure is November (30.14"Hg).
The month with the lowest atmospheric pressure is June (29.95"Hg).
Average wind speed in December
Herndon, VA
- Average wind speed in December: 6.6mph
The windiest month (with the highest average wind speed) is March (7.5mph).
The calmest month (with the lowest average wind speed) is August (4.7mph).
Average humidity in December
Herndon, VA
- Average humidity in December: 78%
The month with the highest relative humidity is December (78%).
The month with the lowest relative humidity is July (70%).
Average rainfall in December
Herndon, VA
- Average rainfall in December: 2.68"
The wettest month (with the highest rainfall) is August (3.78").
The driest month (with the least rainfall) is September (1.93").
Average rainfall days in December
Herndon, VA
- Average rainfall days in December: 10.5 days
The month with the highest number of rainy days is May (17.5 days).
The month with the least rainy days is January (9.3 days).
Average snowfall in December
Herndon, VA
- Average snowfall in December: 1.97"
The month with the highest snowfall is January (3.54").
The months with the least snowfall are May, June, July, August, September and October (0").
Average snowfall days in December
Herndon, VA
- Average snowfall days in December: 2.7 days
The months with the highest number of snowfall days are January and February (5.1 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
Herndon, VA
- Average daylight in December: 9h and 3min
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 30min).
- Average sunshine in December: 5h and 0min
The month with the most sunshine is July (Average sunshine: 10h and 42min).
The months with the least sunshine are January, February and December (Average sunshine: 5h and 0min).
Average sunshine days in December
Herndon, VA
- Average sunshine days in December: 17.5 days
The month with the most sunshine days is November (19.5 days).
The month with the least sunshine days is July (11.8 days).
Average UV index in December
Herndon, VA
- Average UV index in December: 2
The months with the highest UV index are May, 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
Herndon, VA
- Average cloud cover in December: 47
The month with the most cloud cover is March (Cloud cover 48).
The month with the least cloud cover is July (Cloud cover 31).
Average visibility in December
Herndon, VA
- Average visibility in December: 6mi
The months with the highest visibility are January, February, March, April, June, July, August, September, October, November and December (6mi).
The month with the lowest visibility is May (5mi).
Herndon, Virginia, USA
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