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
December brings a drop in Herndon's average high-temperature, falling from a frosty 48.4°F (9.1°C) in November to a wintry 39°F (3.9°C). Herndon experiences an average low-temperature of 28°F (-2.2°C) in the month of December.Humidity
The average relative humidity in December is 81%.Rainfall
In Herndon, Pennsylvania, in December, during 11.8 rainfall days, 2.2" (56mm) of precipitation is typically accumulated. In Herndon, Pennsylvania, during the entire year, the rain falls for 165.3 days and collects up to 30.55" (776mm) of precipitation.Snowfall
January through May, October through December are months with snowfall. In Herndon, Pennsylvania, in December, snow falls for 7 days, with typically accumulated 1.97" (50mm) of snow. In Herndon, Pennsylvania, during the entire year, snow falls for 38.1 days and aggregates up to 17.68" (449mm) of snow.Daylight
With an average of 9h and 18min of daylight, December has the shortest days of the year in Herndon.On the first day of the month, sunrise is at 7:12 am and sunset at 4:40 pm. On the last day of December, in Herndon, sunrise is at 7:31 am and sunset at 4:50 pm EST.
Sunshine
The average sunshine in December in Herndon is 4.4h.UV index
The months with the lowest UV index in Herndon are January through March, November and December, with an average maximum UV index of 2. A UV Index value of 2, and less, symbolizes a low threat to health from unsafe exposure to UV radiation for the ordinary person.Note: In December, the maximum UV index of 2 translates into these guidelines:
Infants, children, and people with sensitive skin should always have protection against lengthy periods of sun exposure. Midday is the peak time for the Sun's radiation; stay in the shade and protect yourself. To cut down UV radiation exposure by about half, sport a wide-brim hat. Take careful note! The UV radiation of the Sun can be nearly doubled by snow reflection.
Frequently asked questions
Is it cold in Herndon during December?
What is the average humidity in December in Herndon?
How much does it rain in Herndon in December?
How many days does it snow in December in Herndon?
What is the month with the shortest days in Herndon?
What is the average length of the day in December in Herndon?
What time are sunrise and sunset in December in Herndon?
How long on average sun shines in December in Herndon?
When is the lowest UV index in Herndon?
How high is the UV index in December in Herndon?
Average temperature in December
Herndon, PA
- Average high temperature in December: 39°F
The warmest month (with the highest average high temperature) is July (82.4°F).
The month with the lowest average high temperature is January (32.9°F).
- Average low temperature in December: 28°F
The month with the highest average low temperature is July (61.2°F).
The coldest month (with the lowest average low temperature) is January (20.1°F).
Average pressure in December
Herndon, PA
- Average pressure in December: 30.1"Hg
The month with the highest atmospheric pressure is November (30.13"Hg).
The month with the lowest atmospheric pressure is June (29.94"Hg).
Average wind speed in December
Herndon, PA
- Average wind speed in December: 7mph
The windiest months (with the highest average wind speed) are March and April (7.8mph).
The calmest month (with the lowest average wind speed) is August (4.5mph).
Average humidity in December
Herndon, PA
- Average humidity in December: 81%
The month with the highest relative humidity is February (82%).
The month with the lowest relative humidity is April (76%).
Average rainfall in December
Herndon, PA
- Average rainfall in December: 2.2"
The wettest month (with the highest rainfall) is May (3.35").
The driest months (with the least rainfall) are February and November (2.09").
Average rainfall days in December
Herndon, PA
- Average rainfall days in December: 11.8 days
The month with the highest number of rainy days is May (18.4 days).
The month with the least rainy days is February (9 days).
Average snowfall in December
Herndon, PA
- Average snowfall in December: 1.97"
The month with the highest snowfall is February (5.67").
The months with the least snowfall are June, July, August and September (0").
Average snowfall days in December
Herndon, PA
- Average snowfall days in December: 7 days
The month with the highest number of snowfall days is January (11.3 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, PA
- 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 18min).
- Average sunshine in December: 4h and 2min
The month with the most sunshine is July (Average sunshine: 10h and 24min).
The month with the least sunshine is February (Average sunshine: 4h and 12min).
Average sunshine days in December
Herndon, PA
- Average sunshine days in December: 14.6 days
The month with the most sunshine days is November (16.4 days).
The month with the least sunshine days is May (9.9 days).
Average UV index in December
Herndon, PA
- 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, March, November and December (UV index 2).
Average cloud cover in December
Herndon, PA
- Average cloud cover in December: 53
The month with the most cloud cover is February (Cloud cover 54).
The month with the least cloud cover is July (Cloud cover 32).
Average visibility in December
Herndon, PA
- Average visibility in December: 5mi
The months with the highest visibility are March, April, June, July and November (6mi).
The months with the lowest visibility are January, February, May, August, September, October and December (5mi).
Herndon, Pennsylvania, USA
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