December weather forecast
Mertztown, PA

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Weather in December

The first month of the winter, December, is also an icy month in Mertztown, Pennsylvania, with temperature in the range of an average low of 28.9°F (-1.7°C) and an average high of 40.3°F (4.6°C).

Temperature

Mertztown's average high-temperature decreases in December, falling from a fresh 50°F (10°C) in November to a wintry 40.3°F (4.6°C). In the month of December, the nighttime temperature in Mertztown dips to a steady average of 28.9°F (-1.7°C).

Humidity

In Mertztown, the average relative humidity in December is 80%.

Rainfall

In Mertztown, during December, the rain falls for 11.2 days and regularly aggregates up to 2.68" (68mm) of precipitation. In Mertztown, during the entire year, the rain falls for 155.8 days and collects up to 30.75" (781mm) of precipitation.

Snowfall

January through May, October through December are months with snowfall. In Mertztown, Pennsylvania, during December, snow falls for 5 days and regularly aggregates up to 2.36" (60mm) of snow. In Mertztown, Pennsylvania, during the entire year, snow falls for 29.4 days and aggregates up to 15.87" (403mm) of snow.

Daylight

With an average of 9h and 18min of daylight, December has the shortest days of the year.
On the first day of the month, sunrise is at 7:07 am and sunset at 4:36 pm. On the last day of December, sunrise is at 7:25 am and sunset at 4:46 pm EST.

Sunshine

The average sunshine in December in Mertztown 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 estimate of 2, and below, represents a minimal health hazard from unprotected exposure to Sun's UV rays for the ordinary person.
Note: A daily maximum UV index of 2 in December translates into the following instructions:
Most people can stay in the Sun for up to 1 hour without burning, apart from children that always must be protected from sun exposure. Stay safe from the Sun's strongest UV rays by limiting exposure during midday. Experience reduced UV exposure by about half when donning a wide-brim hat. Take into account! The reflection from snow can nearly double the Sun's UV radiation intensity.

Frequently asked questions

Is December cold?

During December, Mertztown experiences an average high-temperature of 40.3°F (4.6°C) and a low-temperature of 28.9°F (-1.7°C). The average heat index (a.k.a. 'real feel', 'apparent temperature'), which represents the influence of relative humidity on air temperature, in August is appraised at 86°F (30°C).

What is the average humidity in December?

In December, the average relative humidity is 80%.

How many days does it rain in December?

In Mertztown, in December, during 11.2 rainfall days, 2.68" (68mm) of precipitation is typically accumulated.

How much does it snow in December?

In Mertztown, during December, snow falls for 5 days and regularly aggregates up to 2.36" (60mm) of snow.

What is the month with the shortest days?

December has the shortest days of the year, with an average of 9h and 18min of daylight.

What is the average length of the day in December?

In December, the average day length is 9h and 20min.

When is the sunrise / sunset in December?

In December, on the first day of the month, sunrise is at 7:07 am and sunset at 4:36 pm. On the last day of the month, sunrise is at 7:25 am and sunset at 4:46 pm EST.

How many hours of sunshine does Mertztown have in December?

In December, the average sunshine duration is 4.7h.

What is the month with the lowest UV index in Mertztown?

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

What is the UV index reading 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 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
Mertztown, PA

Average temperature in December - Mertztown, PA
  • Average high temperature in December: 40.3°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 (34.3°F).

  • Average low temperature in December: 28.9°F

The month with the highest average low temperature is July (63.5°F).
The coldest month (with the lowest average low temperature) is January (21.6°F).

Average pressure in December
Mertztown, PA

Average pressure in December - Mertztown, PA
  • Average pressure in December: 30.09"Hg

The month with the highest atmospheric pressure is November (30.12"Hg).
The month with the lowest atmospheric pressure is June (29.94"Hg).

Average wind speed in December
Mertztown, PA

Average wind speed in December - Mertztown, PA
  • Average wind speed in December: 7.6mph

The windiest month (with the highest average wind speed) is March (8.1mph).
The calmest month (with the lowest average wind speed) is August (4.9mph).

Average humidity in December
Mertztown, PA

Average humidity in December - Mertztown, PA
  • Average humidity in December: 80%

The month with the highest relative humidity is February (82%).
The months with the lowest relative humidity are April and July (76%).

Average rainfall in December
Mertztown, PA

Average rainfall in December - Mertztown, PA
  • Average rainfall in December: 2.68"

The wettest month (with the highest rainfall) is April (2.99").
The driest month (with the least rainfall) is September (1.77").

Average rainfall days in December
Mertztown, PA

Average rainfall days in December - Mertztown, PA
  • Average rainfall days in December: 11.2 days

The month with the highest number of rainy days is May (17.3 days).
The month with the least rainy days is January (8.5 days).

Average snowfall in December
Mertztown, PA

Average snowfall in December - Mertztown, PA
  • Average snowfall in December: 2.36"

The month with the highest snowfall is March (4.29").
The months with the least snowfall are June, July, August and September (0").

Average snowfall days in December
Mertztown, PA

Average snowfall days in December - Mertztown, PA
  • Average snowfall days in December: 5 days

The month with the highest number of snowfall days is January (8.8 days).
The months with the least snowfall days are June, July, August and September (0 days).

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

Average daylight in December / Average sunshine in December - Mertztown, 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 18min).

  • Average sunshine in December: 4h and 4min

The month with the most sunshine is July (Average sunshine: 10h and 24min).
The month with the least sunshine is February (Average sunshine: 4h and 24min).

Average sunshine days in December
Mertztown, PA

Average sunshine days in December - Mertztown, PA
  • Average sunshine days in December: 16.6 days

The month with the most sunshine days is November (17.9 days).
The month with the least sunshine days is April (11.2 days).

Average UV index in December
Mertztown, PA

Average UV index in December - Mertztown, PA
  • Average UV index in December: 2

The months with the highest UV index are 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
Mertztown, PA

Average cloud cover in December - Mertztown, PA
  • Average cloud cover in December: 51

The month with the most cloud cover is February (Cloud cover 52).
The month with the least cloud cover is July (Cloud cover 33).

Average visibility in December
Mertztown, PA

Average visibility in December - Mertztown, 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).

Mertztown, Pennsylvania, USA

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