December weather forecastMercersburg, PA
December
Weather in December
December, the first month of the winter in Mercersburg, is also an icy month, with an average temperature ranging between max 40.8°F (4.9°C) and min 28.9°F (-1.7°C).Temperature
The commencement of December involves a temperature shift, with the average high-temperature dropping from a fresh 50.4°F (10.2°C) in November to a wintry 40.8°F (4.9°C). In Mercersburg, December's nights observe an average temperature dip to a subzero cold 28.9°F (-1.7°C).Humidity
The months with the highest humidity are February, May, October and December, with an average relative humidity of 79%.Rainfall
In Mercersburg, during December, the rain falls for 11.1 days and regularly aggregates up to 2.52" (64mm) of precipitation. In Mercersburg, during the entire year, the rain falls for 170.5 days and collects up to 31.02" (788mm) of precipitation.Snowfall
Months with snowfall are January through April, October through December. In Mercersburg, in December, during 5.9 snowfall days, 2.52" (64mm) of snow is typically accumulated. Throughout the year, in Mercersburg, there are 33.6 snowfall days, and 17.91" (455mm) of snow is accumulated.Daylight
December has the shortest days of the year in Mercersburg, with an average of 9h and 24min of daylight.On the first day of the month, sunrise is at 7:14 am and sunset at 4:47 pm. On the last day of December, sunrise is at 7:32 am and sunset at 4:57 pm EST.
Sunshine
The average sunshine in December is 4.7h.UV index
January through March, November and December, with an average maximum UV index of 2, are months with the lowest UV index. A UV Index of 2, and less, symbolizes a minimal health vulnerability from unsafe exposure to UV radiation for the average person.Note: The average daily UV index of 2 in December transforms into the following instructions:
While extended sun exposure does not significantly affect most people, those with sensitive skin, children, and infants should always be protected. Protect yourself from the midday Sun's peak UV radiation by minimizing exposure. Employ a hat with a wide brim for robust protection, cutting UV exposure by half. Remember to consider! The UV radiation from the Sun can be intensified nearly twice by the reflection of snow.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in December
Mercersburg, PA
- Average high temperature in December: 40.8°F
The warmest month (with the highest average high temperature) is July (84.7°F).
The month with the lowest average high temperature is January (35.2°F).
- Average low temperature in December: 28.9°F
The month with the highest average low temperature is July (62.6°F).
The coldest month (with the lowest average low temperature) is January (22.1°F).
Average pressure in December
Mercersburg, PA
- 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
Mercersburg, PA
- Average wind speed in December: 6.8mph
The windiest month (with the highest average wind speed) is January (7.5mph).
The calmest month (with the lowest average wind speed) is August (4.3mph).
Average humidity in December
Mercersburg, PA
- Average humidity in December: 79%
The months with the highest relative humidity are February, May, October and December (79%).
The months with the lowest relative humidity are April and July (75%).
Average rainfall in December
Mercersburg, PA
- Average rainfall in December: 2.52"
The wettest month (with the highest rainfall) is May (3.19").
The driest month (with the least rainfall) is September (2.05").
Average rainfall days in December
Mercersburg, PA
- Average rainfall days in December: 11.1 days
The month with the highest number of rainy days is May (18.8 days).
The month with the least rainy days is November (9.9 days).
Average snowfall in December
Mercersburg, PA
- Average snowfall in December: 2.52"
The month with the highest snowfall is January (5.2").
The months with the least snowfall are May, June, July, August and September (0").
Average snowfall days in December
Mercersburg, PA
- Average snowfall days in December: 5.9 days
The month with the highest number of snowfall days is January (9.9 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
Mercersburg, PA
- Average daylight in December: 9h and 24min
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 24min).
- Average sunshine in December: 4h and 42min
The month with the most sunshine is July (Average sunshine: 10h and 30min).
The month with the least sunshine is January (Average sunshine: 4h and 36min).
Average sunshine days in December
Mercersburg, PA
- Average sunshine days in December: 15.1 days
The month with the most sunshine days is November (18 days).
The month with the least sunshine days is May (10.3 days).
Average UV index in December
Mercersburg, PA
- Average UV index in December: 2
The months with the highest UV index are May, 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
Mercersburg, PA
- Average cloud cover in December: 50
The months with the most cloud cover are January, February and December (Cloud cover 50).
The month with the least cloud cover is July (Cloud cover 31).
Average visibility in December
Mercersburg, PA
- Average visibility in December: 5mi
The months with the highest visibility are April, June, July and November (6mi).
The months with the lowest visibility are January, February, March, May, August, September, October and December (5mi).
