December weather forecastPotomac, MD
December
Weather in December
The first month of the winter, December, is also a frosty month in Potomac, Maryland, with an average temperature ranging between min 32.9°F (0.5°C) and max 45.5°F (7.5°C).Temperature
With the beginning of December, the average high-temperature shows a small decrease, transitioning from a fresh 53.4°F (11.9°C) in November to a chilly 45.5°F (7.5°C). Potomac, during December nights, observes an average temperature of 32.9°F (0.5°C).Humidity
The months with the highest humidity are October and December, with an average relative humidity of 76%.Rainfall
In Potomac, during December, the rain falls for 9.8 days and regularly aggregates up to 2.36" (60mm) of precipitation. Throughout the year, there are 156.5 rainfall days, and 30.71" (780mm) of precipitation is accumulated.Snowfall
Months with snowfall are January through April, November and December. In Potomac, during December, snow falls for 2.5 days and regularly aggregates up to 1.57" (40mm) of snow. Throughout the year, there are 15.5 snowfall days, and 10.24" (260mm) of snow is accumulated.Daylight
With an average of 9h and 30min of daylight, December has the shortest days of the year.On the first day of the month, sunrise is at 7:09 am and sunset at 4:46 pm. On the last day of December, sunrise is at 7:27 am and sunset at 4:56 pm EST.
Sunshine
The average sunshine in December is 5.1h.UV index
January, February, November and December, with an average maximum UV index of 2, are months with the lowest UV index. A UV Index of 2, and less, symbolizes a low health risk from exposure to the Sun's UV radiation for average individuals.Note: The daily high UV index of 2 in December translates into this advice:
Babies, children, and those with sensitive skin should always avoid extended periods in the sun. Midday is when the Sun's radiation is strongest; avoid prolonged exposure during this time. To cut down UV radiation exposure by about half, sport a wide-brim hat. Remember! The Sun's UV radiation can be magnified almost twofold by the reflection of snow.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in December
Potomac, MD
- Average high temperature in December: 45.5°F
The warmest month (with the highest average high temperature) is July (87.4°F).
The month with the lowest average high temperature is January (39.4°F).
- Average low temperature in December: 32.9°F
The month with the highest average low temperature is July (68.5°F).
The coldest month (with the lowest average low temperature) is January (26.4°F).
Average pressure in December
Potomac, MD
- 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
Potomac, MD
- Average wind speed in December: 6.9mph
The windiest month (with the highest average wind speed) is March (7.8mph).
The calmest month (with the lowest average wind speed) is August (4.9mph).
Average humidity in December
Potomac, MD
- Average humidity in December: 76%
The months with the highest relative humidity are October and December (76%).
The month with the lowest relative humidity is July (69%).
Average rainfall in December
Potomac, MD
- Average rainfall in December: 2.36"
The wettest month (with the highest rainfall) is August (3.86").
The driest month (with the least rainfall) is February (1.93").
Average rainfall days in December
Potomac, MD
- Average rainfall days in December: 9.8 days
The month with the highest number of rainy days is August (17.3 days).
The month with the least rainy days is January (8.1 days).
Average snowfall in December
Potomac, MD
- Average snowfall in December: 1.57"
The month with the highest snowfall is March (3.03").
The months with the least snowfall are May, June, July, August, September and October (0").
Average snowfall days in December
Potomac, MD
- Average snowfall days in December: 2.5 days
The month with the highest number of snowfall days is February (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
Potomac, MD
- Average daylight in December: 9h and 30min
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 30min).
- Average sunshine in December: 5h and 6min
The month with the most sunshine is July (Average sunshine: 10h and 48min).
The month with the least sunshine is February (Average sunshine: 5h and 0min).
Average sunshine days in December
Potomac, MD
- Average sunshine days in December: 18.4 days
The month with the most sunshine days is November (19.9 days).
The month with the least sunshine days is May (11.7 days).
Average UV index in December
Potomac, MD
- 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
Potomac, MD
- Average cloud cover in December: 46
The month with the most cloud cover is March (Cloud cover 47).
The month with the least cloud cover is July (Cloud cover 31).
Average visibility in December
Potomac, MD
- 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).
