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
With the onset of December, Mountainside's average high-temperature slightly adjusts, moderately receding from November's fresh 51.1°F (10.6°C) to a cold 42.3°F (5.7°C). Mountainside records an average low of 31.1°F (-0.5°C) throughout the nights in December.Humidity
The months with the highest humidity are February, October and December, with an average relative humidity of 78%.Rainfall
December is the month with the most rainfall. Rain falls for 11.5 days and accumulates 3.19" (81mm) of precipitation.Snowfall
Months with snowfall are January through May, October through December. In December, it is snowing for 4.1 days. Throughout December, 1.46" (37mm) of snow is accumulated. Throughout the year, there are 25.4 snowfall days, and 10.31" (262mm) of snow is accumulated.Daylight
December has the shortest days of the year in Mountainside, with an average of 9h and 18min of daylight.On the first day of the month, sunrise is at 7:02 am and sunset at 4:30 pm. On the last day of December, in Mountainside, sunrise is at 7:21 am and sunset at 4:40 pm EST.
Sunshine
In Mountainside, the average sunshine in December is 4.9h.UV index
The months with the lowest UV index are January through March, November and December, with an average maximum UV index of 2. A UV Index estimate of 2, and below, represents a low health risk from exposure to the Sun's UV radiation for ordinary individuals.Note: In December, the maximum UV index of 2 suggests these recommendations:
Despite the majority tolerating prolonged sun exposure, those with sensitive skin, infants, and children demand continual protection. Around midday, solar radiation is most harmful; hence, exposure should be limited. Tightly woven clothing, when worn loosely, shields effectively against the Sun. Be mindful! The reflection from snow can increase the Sun's UV radiation nearly twice.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
How cold is December?
What is the most humid month?
What is the average humidity in December in Mountainside?
What is the wettest month?
How many days does it rain in December?
How many days does it snow in December?
What is the month with the shortest days?
How many hours of daylight does Mountainside have in December?
What time are sunrise and 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
Mountainside, NJ
- Average high temperature in December: 42.3°F
The warmest month (with the highest average high temperature) is July (84.2°F).
The month with the lowest average high temperature is January (36°F).
- Average low temperature in December: 31.1°F
The month with the highest average low temperature is July (67.5°F).
The coldest month (with the lowest average low temperature) is January (23.9°F).
Average pressure in December
Mountainside, NJ
- Average pressure in December: 30.08"Hg
The month with the highest atmospheric pressure is November (30.11"Hg).
The month with the lowest atmospheric pressure is June (29.93"Hg).
Average wind speed in December
Mountainside, NJ
- Average wind speed in December: 8.1mph
The windiest month (with the highest average wind speed) is March (8.9mph).
The calmest months (with the lowest average wind speed) are July and August (5.7mph).
Average humidity in December
Mountainside, NJ
- Average humidity in December: 78%
The months with the highest relative humidity are February, October and December (78%).
The months with the lowest relative humidity are April and August (73%).
Average rainfall in December
Mountainside, NJ
- Average rainfall in December: 3.19"
The wettest month (with the highest rainfall) is December (3.19").
The driest month (with the least rainfall) is September (1.69").
Average rainfall days in December
Mountainside, NJ
- Average rainfall days in December: 11.5 days
The month with the highest number of rainy days is July (16.5 days).
The month with the least rainy days is January (9.5 days).
Average snowfall in December
Mountainside, NJ
- Average snowfall in December: 1.46"
The month with the highest snowfall is March (3.23").
The months with the least snowfall are June, July, August and September (0").
Average snowfall days in December
Mountainside, NJ
- Average snowfall days in December: 4.1 days
The months with the highest number of snowfall days are January and February (7.3 days).
The months with the least snowfall days are June, July, August and September (0 days).
Average daylight in December /
Average sunshine in December
Mountainside, NJ
- 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 5min
The month with the most sunshine is July (Average sunshine: 10h and 30min).
The month with the least sunshine is February (Average sunshine: 4h and 36min).
Average sunshine days in December
Mountainside, NJ
- Average sunshine days in December: 15.8 days
The month with the most sunshine days is November (18.4 days).
The month with the least sunshine days is June (11.4 days).
Average UV index in December
Mountainside, NJ
- Average UV index in December: 2
The months with the highest UV index are June, July and August (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
Mountainside, NJ
- Average cloud cover in December: 48
The months with the most cloud cover are February, March and December (Cloud cover 48).
The months with the least cloud cover are July and August (Cloud cover 32).
Average visibility in December
Mountainside, NJ
- Average visibility in December: 6mi
The months with the highest visibility are January, February, March, April, June, July, August, September, October, November and December (6mi).
The month with the lowest visibility is May (5mi).
Mountainside, New Jersey, USA
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