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.

Daily High and Low Temperature in December

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The daily average low (blue) and high (red) temperature with percentile bands (inner band from 25th to 75th percentile, outer band from 10th to 90th percentile).

Fraction of Time Spent in Various Temperature Bands in December

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The average fraction of time spent in various temperature bands: frigid (below 15°F), freezing (15°F to 32°F), cold (32°F to 50°F), cool (50°F to 65°F), comfortable (65°F to 75°F), warm (75°F to 85°F), hot (85°F to 100°F) and sweltering (above 100°F).

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.

Daily Hours of Daylight and Twilight in December

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The number of hours during which the Sun is visible (black line), with various degrees of daylight, twilight, and night, indicated by the color bands. From bottom (most yellow) to top (most gray): full daylight, solar twilight (Sun is visible but less than 6° from the horizon), civil twilight (Sun is not visible but is less than 6° below the horizon), nautical twilight (Sun is between 6° and 12° below the horizon), astronomical twilight (Sun is between 12° and 18° below the horizon), and full night.

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.

Daily Sunrise & Sunset with Twilight in December

The solar day over the course of the year 2012 . From bottom to top, the black lines are the previous solar midnight, sunrise, solar noon, sunset, and the next solar midnight. The day, twilights (solar, civil, nautical, and astronomical), and night are indicated by the color bands from yellow to gray.

The median cloud cover is 89% (mostly cloudy) and does not vary substantially over the course of the month.

Median Cloud Cover in December

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The median daily cloud cover (black line) with percentile bands (inner band from 40th to 60th percentile, outer band from 25th to 75th percentile).

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.

Cloud Cover Types in December

The fraction of time spent in each of the five sky cover categories. From top (most blue) to bottom (most gray), the categories are clear, mostly clear, partly cloudy, mostly cloudy, and overcast. Pink indicates missing data. Outside of the United States clear skies are often reported ambiguously, leading them to be lumped in with the missing data.

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.

Probability of Precipitation at Some Point in the Day in December

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The fraction of days in which various types of precipitation are observed. If more than one type of precipitation is reported in a given day, the more severe precipitation is counted. For example, if light rain is observed in the same day as a thunderstorm, that day counts towards the thunderstorm totals. The order of severity is from the top down in this graph, with the most severe at the bottom.

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.

Types of Precipitation Throughout December

Relative frequency of various types of precipitation over the course of a typical December.

The likelihood of snow falling is highest around December 27, occurring in 50% of days.

Probability of Snow Fall Being Reported in a Given Day in December

Probability that snow will be reported at least once in a given day.

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.

Chance of at Least Some Snow on the Ground in December

The probability that there is snow on the ground.

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.

Snow Depth When there is Snow on the Ground in December

The median depth of snow during times when there is at least some snow on the ground, with percentile bands (inner band from 25th to 75th percentile, outer band from 10th to 90th percentile).

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.

Relative Humidity in December

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The average daily high (blue) and low (brown) relative humidity with percentile bands (inner bands from 25th to 75th percentile, outer bands from 10th to 90th percentile).

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).

Dew Point in December

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The daily average low (blue) and high (red) dew point with percentile bands (inner band from 25th to 75th percentile, outer band from 10th to 90th percentile).

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).

Wind Speed in December

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The average daily minimum (red), maximum (green), and average (black) wind speed with percentile bands (inner band from 25th to 75th percentile, outer band from 10th to 90th percentile).

Wind Directions in December

The fraction of time spent with the wind blowing from the various directions over the entire year. Values do not sum to 100% because the wind direction is undefined when the wind speed is zero.

Fraction of Time Spent with Various Wind Directions in December

The fraction of time spent with the wind blowing from the various directions on a daily basis. Stacked values do not always sum to 100% because the wind direction is undefined when the wind speed is zero.