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 Southwest's average high-temperature, falling from a chilly 48.9°F (9.4°C) in November to an icy 39.2°F (4°C). The low-temperature average for Southwest during December stands at a subzero cold 27.7°F (-2.4°C).Humidity
In Southwest, the average relative humidity in December is 84%.Rainfall
In December, the rain falls for 13.1 days. Throughout December, 3.03" (77mm) of precipitation is accumulated. In Southwest, during the entire year, the rain falls for 185.4 days and collects up to 34.02" (864mm) of precipitation.Snowfall
Months with snowfall are January through May, October through December. In December, it is snowing for 12.8 days. Throughout December, 6.1" (155mm) of snow is accumulated. In Southwest, during the entire year, snow falls for 63.2 days and aggregates up to 29.02" (737mm) of snow.Daylight
December has the shortest days of the year, with an average of 9h and 24min of daylight.On the first day of the month, sunrise is at 7:21 am and sunset at 4:52 pm. On the last day of December, sunrise is at 7:40 am and sunset at 5:02 pm EST.
Sunshine
In December, the average sunshine is 3.6h.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 estimate of 2, and below, represents a low threat to health from exposure to the Sun's UV rays for the average person.Note: The maximum UV index, 2 during December, leads to the following recommendations:
Extended time in the sun generally does not harm most, but those with sensitive skin, infants, and children should always be protected. Midday is when the Sun's radiation is strongest; avoid prolonged exposure during this time. Fend off the sun's harsh rays with appropriate clothing, a wide-brim hat, and UV-protective sunglasses. Heads up! The UV radiation from the Sun can almost be doubled by snow reflection.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
How cold does it get in December?
What is the average humidity in December in Southwest?
How much does it rain in December?
How many days does it snow in December in Southwest?
What is the month with the shortest days in Southwest?
What is the average length of the day in December?
When is the sunrise / sunset in December?
How long on average sun shines in December?
When is the lowest UV index?
What is the UV index intensity in December?
Average temperature in December
Southwest, PA
- Average high temperature in December: 39.2°F
The warmest month (with the highest average high temperature) is July (82°F).
The month with the lowest average high temperature is January (33.3°F).
- Average low temperature in December: 27.7°F
The month with the highest average low temperature is July (60.4°F).
The coldest month (with the lowest average low temperature) is January (20.3°F).
Average pressure in December
Southwest, 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
Southwest, PA
- Average wind speed in December: 7.9mph
The windiest month (with the highest average wind speed) is January (8.5mph).
The calmest month (with the lowest average wind speed) is August (4.8mph).
Average humidity in December
Southwest, PA
- Average humidity in December: 84%
The months with the highest relative humidity are January and February (85%).
The months with the lowest relative humidity are April, July and August (77%).
Average rainfall in December
Southwest, PA
- Average rainfall in December: 3.03"
The wettest month (with the highest rainfall) is May (3.66").
The driest month (with the least rainfall) is November (2.01").
Average rainfall days in December
Southwest, PA
- Average rainfall days in December: 13.1 days
The month with the highest number of rainy days is May (22 days).
The month with the least rainy days is January (9.8 days).
Average snowfall in December
Southwest, PA
- Average snowfall in December: 6.1"
The month with the highest snowfall is January (7.09").
The months with the least snowfall are June, July, August and September (0").
Average snowfall days in December
Southwest, PA
- Average snowfall days in December: 12.8 days
The month with the highest number of snowfall days is January (17.3 days).
The months with the least snowfall days are June, July, August and September (0 days).
Average daylight in December /
Average sunshine in December
Southwest, 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 4min
The month with the most sunshine is August (Average sunshine: 10h and 0min).
The month with the least sunshine is January (Average sunshine: 3h and 0min).
Average sunshine days in December
Southwest, PA
- Average sunshine days in December: 9.7 days
The month with the most sunshine days is November (13.5 days).
The month with the least sunshine days is January (6.5 days).
Average UV index in December
Southwest, PA
- Average UV index in December: 2
The month with the highest UV index is 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
Southwest, PA
- Average cloud cover in December: 64
The month with the most cloud cover is January (Cloud cover 69).
The month with the least cloud cover is August (Cloud cover 35).
Average visibility in December
Southwest, PA
- Average visibility in December: 5mi
The month with the highest visibility is April (6mi).
The months with the lowest visibility are January and February (4mi).
Southwest, Pennsylvania, USA
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