This report describes the typical weather at the Reykjavík Airport (Reykjavík, Iceland) weather station over the course of an average January. 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 January is characterized by essentially constant daily high temperatures, with daily highs around 36°F throughout the month, exceeding 45°F or dropping below 27°F only one day in ten.
Over the course of January, the length of the day is very rapidly increasing. From the start to the end of the month, the length of the day increases by 2:32 hours, implying an average day-over-day increase of 4.9 minutes.
The shortest day of the month is January 2 with 4:24 hours of daylight; the longest day is January 31 with 6:56 hours of daylight.
The earliest sunrise is at 10:13am on January 31; the latest sunset is at 5:09pm on January 31; the latest sunrise is at 11:19am on January 2; the earliest sunset is at 3:43pm on January 1.
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 January 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 58% of the time.
The average probability that some form of precipitation will be observed in a given day is 77%, with little variation over the course of the month.
Throughout January, the most common forms of precipitation are moderate snow, moderate rain, and light snow.
Moderate snow is the most severe precipitation observed during 52% of those days with precipitation. It is most likely around January 22, when it is observed during 41% of all days.
Moderate rain is the most severe precipitation observed during 23% of those days with precipitation. It is most likely around January 2, when it is observed during 18% of all days.
Light snow is the most severe precipitation observed during 12% of those days with precipitation. It is most likely around January 31, when it is observed during 10% of all days.
The likelihood of snow falling is highest around January 31, occurring in 52% of days.
Accumulation at this location in January is extremely unlikely. The chances of there being snow on the ground are highest around January 13, occurring 5% of the time.
The snow is typically at its deepest on January 27, with a median depth of 3.1"; the depth exceeds 3.7" only one year out of ten.
The relative humidity typically ranges from 65% (mildly humid) to 90% (very humid) over the course of a typical January, rarely dropping below 51% (mildly humid) and reaching as high as 100% (very humid).
The air is driest around January 1, at which time the relative humidity drops below 73% (humid) three days out of four; it is most humid around January 23, 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 January, the dew point typically varies from 20°F (dry) to 31°F (dry) and is rarely below 7°F (dry) or above 42°F (dry).
Over the course of January typical wind speeds vary from 4 mph to 26 mph (light breeze to strong breeze), rarely exceeding 41 mph (gale).
The highest average wind speed of 18 mph (fresh breeze) occurs around January 1, at which time the average daily maximum wind speed is 25 mph (strong breeze).
The lowest average wind speed of 15 mph (moderate breeze) occurs around January 10, at which time the average daily maximum wind speed is 25 mph (strong breeze).