This report describes the typical weather at the Ted Stevens Anchorage International Airport (Anchorage, Alaska, United States) weather station over the course of an average December. It is based on the historical records from 1974 to 2012. Earlier records are either unavailable or unreliable.
Anchorage, Alaska has a continental climate with short dry cool summers. The area within 25 mi of this station is covered by forests (47%), oceans and seas (35%), tundra (11%), shrublands (2%), and marshes (2%).
The month of December is characterized by gradually falling daily high temperatures, with daily highs around 24°F throughout the month, exceeding 38°F or dropping below 8°F only one day in ten.
Over the course of December, the length of the day is essentially constant. The shortest day of the month is December 23 with 5:26 hours of daylight; the longest day is December 1 with 6:06 hours of daylight.
The earliest sunrise is at 9:46am on December 1; the latest sunset is at 3:52pm on December 31; the latest sunrise is at 10:16am on December 23; the earliest sunset is at 3:40pm on December 18.
Daylight savings time is observed in 2012 but it neither starts nor ends in December, so the entire month is in standard time.
The median cloud cover is 97% (overcast) and does not vary substantially over the course of the month.
On December 16, a representative day, the sky is clear or mostly clear 19% of the time, partly cloudy 12% of the time, and mostly cloudy or overcast 69% of the time.
The average probability that some form of precipitation will be observed in a given day is 61%, with little variation over the course of the month.
Throughout December, the most common forms of precipitation are light snow and moderate snow.
Light snow is the most severe precipitation observed during 68% of those days with precipitation. It is most likely around December 27, when it is observed during 42% of all days.
Moderate snow is the most severe precipitation observed during 19% of those days with precipitation. It is most likely around December 23, when it is observed during 12% of all days.
The likelihood of snow falling is highest around December 25, occurring in 55% of days.
Accumulation at this location in December is likely. The chances of there being snow on the ground are highest around December 22, occurring 76% of the time.
The snow is typically at its deepest on December 30, with a median depth of 8.6"; the depth exceeds 19.1" only one year out of ten.
The relative humidity typically ranges from 67% (mildly humid) to 90% (very humid) over the course of a typical December, rarely dropping below 48% (comfortable) and reaching as high as 98% (very humid).
The air is driest around December 31, at which time the relative humidity drops below 76% (humid) three days out of four; it is most humid around December 15, rising above 87% (very humid) three days out of four.
Dew point is often a better measure of how comfortable a person will find the weather than relative humidity because it more directly relates to whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid.
Over the course of a typical December, the dew point typically varies from 6°F (dry) to 19°F (dry) and is rarely below -12°F (dry) or above 32°F (dry).
Over the course of December typical wind speeds vary from 0 mph to 12 mph (calm to gentle breeze), rarely exceeding 20 mph (fresh breeze).
The highest average wind speed of 7 mph (light breeze) occurs around December 6, at which time the average daily maximum wind speed is 12 mph (gentle breeze).
The lowest average wind speed of 6 mph (light breeze) occurs around December 30, at which time the average daily maximum wind speed is 11 mph (gentle breeze).