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
A decrease in the average high-temperature is observed during December, shifting from a chilly 49.3°F (9.6°C) in November to a wintry 39.7°F (4.3°C). In Castle Shannon, December's nights observe an average temperature dip to a freezing cold 28.2°F (-2.1°C).Humidity
In December, the average relative humidity is 83%.Rainfall
In Castle Shannon, in December, it is raining for 10.7 days, with typically 2.09" (53mm) of accumulated precipitation. Throughout the year, there are 164 rainfall days, and 26.89" (683mm) of precipitation is accumulated.Snowfall
January through April, October through December are months with snowfall. In Castle Shannon, in December, during 11.8 snowfall days, 2.64" (67mm) of snow is typically accumulated. Throughout the year, there are 53.3 snowfall days, and 13.27" (337mm) of snow is accumulated.Daylight
With an average of 9h and 24min of daylight, December has the shortest days of the year.On the first day of the month, sunrise is at 7:24 am and sunset at 4:54 pm. On the last day of December, sunrise is at 7:42 am and sunset at 5:03 pm EST.
Sunshine
In December, the average sunshine is 3.3h.UV index
December is the month with the lowest UV index, with an average maximum UV index of 1. A UV Index estimate of 2, and below, represents a low threat to health from unprotected exposure to Sun's UV rays for the ordinary person.Note: A maximum high UV index of 1 in December translates into the following recommendations:
People with sensitive skin, children, and babies should always be protected from prolonged sun exposure. The Sun's radiation is especially intense around midday; try to stay in shade during this period. Wearing a wide-brim hat can block approximately 50% of UV radiation, protecting the eyes. On your guard! Snow's reflection 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 it in December?
What is the average humidity in December?
How many days 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 in Castle Shannon?
What time are sunrise and sunset in December?
How many hours of sunshine does Castle Shannon have in December?
When is the lowest UV index?
How high is the UV index in December?
Average temperature in December
Castle Shannon, PA
- Average high temperature in December: 39.7°F
The warmest month (with the highest average high temperature) is July (83.8°F).
The month with the lowest average high temperature is January (33.4°F).
- Average low temperature in December: 28.2°F
The month with the highest average low temperature is July (63°F).
The coldest month (with the lowest average low temperature) is January (20.8°F).
Average pressure in December
Castle Shannon, PA
- Average pressure in December: 30.11"Hg
The month with the highest atmospheric pressure is November (30.13"Hg).
The month with the lowest atmospheric pressure is June (29.95"Hg).
Average wind speed in December
Castle Shannon, PA
- Average wind speed in December: 7.3mph
The windiest month (with the highest average wind speed) is January (7.9mph).
The calmest month (with the lowest average wind speed) is August (4.7mph).
Average humidity in December
Castle Shannon, PA
- Average humidity in December: 83%
The months with the highest relative humidity are January and February (84%).
The month with the lowest relative humidity is August (73%).
Average rainfall in December
Castle Shannon, PA
- Average rainfall in December: 2.09"
The wettest month (with the highest rainfall) is May (3.07").
The driest month (with the least rainfall) is November (1.61").
Average rainfall days in December
Castle Shannon, PA
- Average rainfall days in December: 10.7 days
The month with the highest number of rainy days is May (18.4 days).
The month with the least rainy days is January (8.5 days).
Average snowfall in December
Castle Shannon, PA
- Average snowfall in December: 2.64"
The month with the highest snowfall is January (3.46").
The months with the least snowfall are May, June, July, August and September (0").
Average snowfall days in December
Castle Shannon, PA
- Average snowfall days in December: 11.8 days
The month with the highest number of snowfall days is January (16.3 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
Castle Shannon, 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 24min).
- Average sunshine in December: 3h and 2min
The month with the most sunshine is August (Average sunshine: 10h and 6min).
The month with the least sunshine is January (Average sunshine: 2h and 54min).
Average sunshine days in December
Castle Shannon, PA
- Average sunshine days in December: 11 days
The month with the most sunshine days is November (16.4 days).
The month with the least sunshine days is February (9.5 days).
Average UV index in December
Castle Shannon, PA
- Average UV index in December: 1
The months with the highest UV index are June and July (UV index 6).
The month with the lowest UV index is December (UV index 1).
Average cloud cover in December
Castle Shannon, PA
- Average cloud cover in December: 66
The month with the most cloud cover is January (Cloud cover 69).
The month with the least cloud cover is August (Cloud cover 34).
Average visibility in December
Castle Shannon, PA
- Average visibility in December: 5mi
The months with the highest visibility are April, June, July, August and November (6mi).
The months with the lowest visibility are January, February, March, May, September, October and December (5mi).
Castle Shannon, Pennsylvania, USA
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