December weather forecast
Sylmar, PA

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Weather in December

The first month of the winter, December, is also a frosty month in Sylmar, Pennsylvania, with an average temperature ranging between min 31.3°F (-0.4°C) and max 43.2°F (6.2°C).

Temperature

The transition to December results in a modest reduction in average high-temperature, moving from a cool 51.6°F (10.9°C) in November to a frosty 43.2°F (6.2°C). December's nights observe an average temperature of 31.3°F (-0.4°C).

Humidity

The average relative humidity in December is 79%.

Rainfall

In Sylmar, Pennsylvania, during December, the rain falls for 8.6 days and regularly aggregates up to 1.18" (30mm) of precipitation. Throughout the year, there are 130.4 rainfall days, and 16.3" (414mm) of precipitation is accumulated.

Snowfall

January through April, November and December are months with snowfall. In Sylmar, during December, snow falls for 2.5 days and regularly aggregates up to 0.59" (15mm) of snow. Throughout the year, there are 16.2 snowfall days, and 5.35" (136mm) of snow is accumulated.

Daylight

December has the shortest days of the year, with an average of 9h and 24min of daylight.
On the first day of December, sunrise is at 7:06 am and sunset at 4:40 pm. On the last day of the month, sunrise is at 7:24 am and sunset at 4:49 pm EST.

Sunshine

The average sunshine in December is 5h.

UV index

The months with the lowest UV index are January, February, November and December, with an average maximum UV index of 2. A UV Index of 2, and less, symbolizes a low health risk from unsafe exposure to UV radiation for the average person.
Note: An average UV index of 2 in December transforms into this advice:
Babies, children, and those with sensitive skin should always avoid extended periods in the sun. The Sun's radiation is especially intense around midday; try to stay in shade during this period. For minimizing sun-related eye damage, always choose sunglasses with UVA and UVB coverage. Foresee this! The reflection from snow can nearly double the intensity of UV radiation from the Sun.
Updated: Jul 15, 2024
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate

Frequently asked questions

Is December cold?

In Sylmar, 43.2°F (6.2°C) is the average high-temperature and 31.3°F (-0.4°C) is the average low-temperature during December. In August, the average heat index (a.k.a. 'real feel', 'feels like'), which combines relative humidity and air temperature, is calculated to be 87.8°F (31°C).

What is the average humidity in December?

In Sylmar, the average relative humidity in December is 79%.

How much does it rain in December?

In Sylmar, in December, during 8.6 rainfall days, 1.18" (30mm) of precipitation is typically accumulated.

How many days does it snow in December?

In Sylmar, during December, snow falls for 2.5 days and regularly aggregates up to 0.59" (15mm) of snow.

What is the month with the shortest days?

With an average of 9h and 24min of daylight, December has the shortest days of the year.

How many hours of daylight does Sylmar have in December?

In December, the average day length in Sylmar is 9h and 25min.

When is the sunrise / sunset in December?

On the first day of December in Sylmar, sunrise is at 7:06 am and sunset at 4:40 pm. On the last day of the month, sunrise is at 7:24 am and sunset at 4:49 pm EST.

How long on average sun shines in December?

In December, the average sunshine duration in Sylmar is 5h.

What is the month with the lowest UV index?

The months with the lowest UV index are January, February, November and December, with an average maximum UV index of 2.

How high is the UV index in December?

In December, the average daily maximum UV index is 2. A UV Index reading of 2, and below, represents a low health threat from unsafe exposure to Sun's UV rays.
Average humidity
Average rainfall days
Average snowfall days
Average daylight
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in December
Sylmar, PA

Average temperature in December - Sylmar, PA
  • Average high temperature in December: 43.2°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 (36.7°F).

  • Average low temperature in December: 31.3°F

The month with the highest average low temperature is July (65.8°F).
The coldest month (with the lowest average low temperature) is January (24.6°F).

Average pressure in December
Sylmar, PA

Average pressure in December - Sylmar, 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
Sylmar, PA

Average wind speed in December - Sylmar, PA
  • Average wind speed in December: 8.3mph

The windiest months (with the highest average wind speed) are January, February and March (8.9mph).
The calmest month (with the lowest average wind speed) is August (5.2mph).

Average humidity in December
Sylmar, PA

Average humidity in December - Sylmar, PA
  • Average humidity in December: 79%

The month with the highest relative humidity is May (81%).
The months with the lowest relative humidity are January, March, April and November (76%).

Average rainfall in December
Sylmar, PA

Average rainfall in December - Sylmar, PA
  • Average rainfall in December: 1.18"

The wettest month (with the highest rainfall) is August (2.36").
The driest month (with the least rainfall) is January (0.91").

Average rainfall days in December
Sylmar, PA

Average rainfall days in December - Sylmar, PA
  • Average rainfall days in December: 8.6 days

The month with the highest number of rainy days is May (15.1 days).
The month with the least rainy days is January (6 days).

Average snowfall in December
Sylmar, PA

Average snowfall in December - Sylmar, PA
  • Average snowfall in December: 0.59"

The month with the highest snowfall is March (1.61").
The months with the least snowfall are May, June, July, August, September and October (0").

Average snowfall days in December
Sylmar, PA

Average snowfall days in December - Sylmar, PA
  • Average snowfall days in December: 2.5 days

The month with the highest number of snowfall days is January (4.8 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
Sylmar, PA

Average daylight in December / Average sunshine in December - Sylmar, PA
  • Average daylight in December: 9h and 2min

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: 5h and 0min

The month with the most sunshine is July (Average sunshine: 10h and 36min).
The month with the least sunshine is February (Average sunshine: 4h and 48min).

Average sunshine days in December
Sylmar, PA

Average sunshine days in December - Sylmar, PA
  • Average sunshine days in December: 19.6 days

The month with the most sunshine days is November (21.8 days).
The month with the least sunshine days is June (13.2 days).

Average UV index in December
Sylmar, PA

Average UV index in December - Sylmar, PA
  • 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
Sylmar, PA

Average cloud cover in December - Sylmar, PA
  • Average cloud cover in December: 46

The months with the most cloud cover are February, March and May (Cloud cover 47).
The month with the least cloud cover is July (Cloud cover 32).

Average visibility in December
Sylmar, PA

Average visibility in December - Sylmar, PA
  • Average visibility in December: 6mi

The months with the highest visibility are January, February, March, April, June, July, October, November and December (6mi).
The months with the lowest visibility are May, August and September (5mi).

Sylmar, Pennsylvania, USA

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