This report describes the typical weather at the Reykjavík Airport (Reykjavík, Iceland) weather station over the course of an average December. It is based on the historical records from 1979 to 2012. Earlier records are either unavailable or unreliable.
Reykjavík has a humid subarctic continental climate with cool summers and no dry season. The area within 25 mi of this station is covered by oceans and seas (39%), shrublands (34%), forests (19%), and tundra (4%).
The month of December is characterized by gradually falling daily high temperatures, with daily highs around 37°F throughout the month, exceeding 47°F or dropping below 26°F only one day in ten.
Over the course of December, the length of the day is gradually decreasing. The shortest day of the month is December 23 with 4:08 hours of daylight; the longest day is December 1 with 4:58 hours of daylight.
The earliest sunrise is at 10:48am on December 1; the latest sunset is at 3:46pm on December 1; the latest sunrise is at 11:24am on December 25; the earliest sunset is at 3:27pm on December 16.
Daylight savings time (DST) is not observed in 2012.
The median cloud cover is 89% (mostly cloudy) and does not vary substantially over the course of the month.
On December 16, a representative day, the sky is clear or mostly clear 18% of the time, partly cloudy 16% of the time, and mostly cloudy or overcast 57% of the time.
The average probability that some form of precipitation will be observed in a given day is 76%, with little variation over the course of the month.
Throughout December, the most common forms of precipitation are moderate snow, moderate rain, and light snow.
Moderate snow is the most severe precipitation observed during 47% of those days with precipitation. It is most likely around December 30, when it is observed during 38% of all days.
Moderate rain is the most severe precipitation observed during 26% of those days with precipitation. It is most likely around December 1, when it is observed during 23% of all days.
Light snow is the most severe precipitation observed during 13% of those days with precipitation. It is most likely around December 21, when it is observed during 10% of all days.
The likelihood of snow falling is highest around December 27, occurring in 50% of days.
Accumulation at this location in December is very unlikely. The chances of there being snow on the ground are highest around December 27, occurring 5% of the time.
The snow is typically at its deepest on December 27, with a median depth of 2.2"; the depth exceeds 2.7" only one year out of ten.
The relative humidity typically ranges from 64% (mildly humid) to 90% (very humid) over the course of a typical December, rarely dropping below 50% (mildly humid) and reaching as high as 100% (very humid).
The air is driest around December 25, at which time the relative humidity drops below 73% (humid) three days out of four; it is most humid around December 3, rising above 86% (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 19°F (dry) to 33°F (dry) and is rarely below 6°F (dry) or above 44°F (dry).
Over the course of December typical wind speeds vary from 4 mph to 26 mph (light breeze to strong breeze), rarely exceeding 40 mph (gale).
The highest average wind speed of 20 mph (fresh breeze) occurs around December 19, at which time the average daily maximum wind speed is 26 mph (strong breeze).
The lowest average wind speed of 15 mph (moderate breeze) occurs around December 1, at which time the average daily maximum wind speed is 23 mph (fresh breeze).