December weather forecast
Washington, PA

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Weather in December

December announces the return of winter in Washington, with average temperatures dropping to a wintery 40.1°F (4.5°C). Amid the festive cheer, the weather gets frostier, with the reappearance of substantial snowfall at 0.83" (21mm). The city, blanketed by white fluff, takes on a winter wonderland persona with lights twinkling against the snow-clad background. The shorter days and longer nights become noticeable, complemented by the wintry cold and early sunsets. As the final month of the year and the onset of winter, December brings the climatic cycles full circle, rounding off Washington's weather story with a snowy flourish.

Temperature

The onset of December brings a small change in high-temperatures, falling from a frosty 49.5°F (9.7°C) in November to a wintry 40.1°F (4.5°C). Washington experiences a consistent average temperature of 28.6°F (-1.9°C) throughout the nights in December.

Humidity

The average relative humidity in December is 84%.

Rainfall

In Washington, in December, it is raining for 9.4 days, with typically 1.06" (27mm) of accumulated precipitation. In Washington, during the entire year, the rain falls for 143 days and collects up to 14.8" (376mm) of precipitation.

Snowfall

Months with snowfall are January through May, October through December. In Washington, during December, snow falls for 6.5 days and regularly aggregates up to 0.83" (21mm) of snow. Throughout the year, there are 33.5 snowfall days, and 4.88" (124mm) 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 December, sunrise is at 7:24 am and sunset at 4:55 pm. On the last day of the month, sunrise is at 7:43 am and sunset at 5:05 pm EST.

Sunshine

The average sunshine in December is 3.5h.

UV index

With an average maximum UV index of 1, December is the month with the lowest UV index. A UV Index value of 2, and less, symbolizes a low health risk from exposure to the Sun's UV rays for the average person.
Note: A maximum high daily UV index of 1 during December translates into the following directions:
Extended sunlight exposure does not pose significant problems for most people, except for children, infants, and people with fair skin who always need shielding. To prevent harmful UV exposure, minimize direct contact with the Sun around midday. Prioritize a wide-brim hat for comprehensive sun defense for your face, neck, eyes, and ears. Be informed! The Sun's UV radiation can be nearly doubled due to the reflection from snow.
Updated: Aug 28, 2024
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate

Frequently asked questions

Is it cold during December?

The high-temperature during December is 40.1°F (4.5°C) and the low-temperature is 28.6°F (-1.9°C). The average heat index (a.k.a. 'apparent temperature', 'real feel'), which factors the actual air temperature with the relative humidity, in August is appraised at 87.8°F (31°C).

What is the average humidity in December?

In Washington, the average relative humidity in December is 84%.

How many days does it rain in December in Washington?

In Washington, in December, it is raining for 9.4 days, with typically 1.06" (27mm) of accumulated precipitation.

How much does it snow in Washington in December?

In December, it is snowing for 6.5 days. Throughout December, 0.83" (21mm) of snow is accumulated.

What is the month with the shortest days?

The month with the shortest days is December, with an average of 9h and 24min of daylight.

What is the average length of the day in December?

In Washington, Pennsylvania, the average day length in December is 9h and 22min.

When is the sunrise / sunset in December?

In December, on the first day of the month, sunrise is at 7:24 am and sunset at 4:55 pm. On the last day of the month, sunrise is at 7:43 am and sunset at 5:05 pm EST.

How long on average sun shines in December?

The average sunshine duration in December is 3.5h.

What is the month with the lowest UV index?

December is the month with the lowest UV index, with an average maximum UV index of 1.

What is the UV index intensity in December?

In December, the average daily maximum UV index is 1. A UV Index reading of 2, and below, represents a minimal health vulnerability from unprotected exposure to UV radiation.
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
Washington, PA

Average temperature in December - Washington, PA
  • Average high temperature in December: 40.1°F

The warmest month (with the highest average high temperature) is July (83.3°F).
The month with the lowest average high temperature is January (33.6°F).

  • Average low temperature in December: 28.6°F

The month with the highest average low temperature is July (61.9°F).
The coldest month (with the lowest average low temperature) is January (20.8°F).

Average pressure in December
Washington, PA

Average pressure in December - Washington, 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
Washington, PA

Average wind speed in December - Washington, PA
  • Average wind speed in December: 7.1mph

The windiest month (with the highest average wind speed) is January (7.8mph).
The calmest month (with the lowest average wind speed) is August (4.5mph).

Average humidity in December
Washington, PA

Average humidity in December - Washington, PA
  • Average humidity in December: 84%

The month with the highest relative humidity is February (85%).
The months with the lowest relative humidity are April, July and August (77%).

Average rainfall in December
Washington, PA

Average rainfall in December - Washington, PA
  • Average rainfall in December: 1.06"

The wettest month (with the highest rainfall) is July (1.65").
The driest months (with the least rainfall) are January and November (0.94").

Average rainfall days in December
Washington, PA

Average rainfall days in December - Washington, PA
  • Average rainfall days in December: 9.4 days

The month with the highest number of rainy days is May (17.2 days).
The month with the least rainy days is February (7.3 days).

Average snowfall in December
Washington, PA

Average snowfall in December - Washington, PA
  • Average snowfall in December: 0.83"

The month with the highest snowfall is February (1.26").
The months with the least snowfall are June, July, August and September (0").

Average snowfall days in December
Washington, PA

Average snowfall days in December - Washington, PA
  • Average snowfall days in December: 6.5 days

The month with the highest number of snowfall days is January (9.8 days).
The months with the least snowfall days are June, July, August and September (0 days).

Average daylight in December /
Average sunshine in December
Washington, PA

Average daylight in December / Average sunshine in December - Washington, 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 3min

The month with the most sunshine is August (Average sunshine: 10h and 12min).
The month with the least sunshine is January (Average sunshine: 3h and 0min).

Average sunshine days in December
Washington, PA

Average sunshine days in December - Washington, PA
  • Average sunshine days in December: 17.5 days

The month with the most sunshine days is November (19.1 days).
The month with the least sunshine days is May (11.8 days).

Average UV index in December
Washington, PA

Average UV index in December - Washington, PA
  • Average UV index in December: 1

The months with the highest UV index are June, July and August (UV index 6).
The month with the lowest UV index is December (UV index 1).

Average cloud cover in December
Washington, PA

Average cloud cover in December - Washington, PA
  • Average cloud cover in December: 64

The month with the most cloud cover is January (Cloud cover 68).
The month with the least cloud cover is August (Cloud cover 33).

Average visibility in December
Washington, PA

Average visibility in December - Washington, PA
  • Average visibility in December: 5mi

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

Washington, Pennsylvania, USA

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