This report describes the typical weather at the Slave Lake Airport (Slave Lake, Alberta, Canada) weather station over the course of an average December. It is based on the historical records from 1978 to 2012. Earlier records are either unavailable or unreliable.
Slave Lake, Alberta has a humid subarctic continental climate with cool summers and no dry season. The area within 25 mi of this station is covered by forests (84%), lakes and rivers (12%), and croplands (4%).
The month of December is characterized by falling daily high temperatures, with daily highs decreasing from 22°F to 15°F over the course of the month, exceeding 39°F or dropping below -7°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 15 with 7:08 hours of daylight; the longest day is December 1 with 7:30 hours of daylight.
The earliest sunrise is at 8:43am on December 1; the latest sunset is at 4:19pm on December 31; the latest sunrise is at 9:07am on December 27; the earliest sunset is at 4:08pm on December 14.
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 ranges from 58% (partly cloudy) to 64% (partly cloudy).
On December 16, a representative day, the sky is clear or mostly clear 45% of the time, partly cloudy 5% of the time, and mostly cloudy or overcast 47% of the time.
The average probability that some form of precipitation will be observed in a given day is 52%, 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 80% of those days with precipitation. It is most likely around December 31, when it is observed during 43% of all days.
Moderate snow is the most severe precipitation observed during 10% of those days with precipitation. It is most likely around December 14, when it is observed during 6% of all days.
The likelihood of snow falling is highest around December 31, occurring in 50% of days.
Accumulation at this location in December is just less likely than not. The chances of there being snow on the ground are highest around December 31, occurring 38% of the time.
The snow is typically at its deepest on December 23, with a median depth of 5.3"; the depth exceeds 9.0" only one year out of ten.
The relative humidity typically ranges from 65% (mildly humid) to 89% (very humid) over the course of a typical December, rarely dropping below 51% (mildly humid) and reaching as high as 98% (very humid).
The air is driest around December 31, at which time the relative humidity drops below 73% (humid) three days out of four; it is most humid around December 10, rising above 85% (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 15°F (dry) and is rarely below -29°F (dry) or above 30°F (dry).
Over the course of December typical wind speeds vary from 0 mph to 17 mph (calm to moderate breeze), rarely exceeding 28 mph (strong breeze).
The highest average wind speed of 9 mph (gentle breeze) occurs around December 12, at which time the average daily maximum wind speed is 17 mph (moderate breeze).
The lowest average wind speed of 9 mph (gentle breeze) occurs around December 28, at which time the average daily maximum wind speed is 16 mph (moderate breeze).