This report describes the typical weather at the Dane County Regional Airport (Madison, Wisconsin, 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.
Madison, Wisconsin has a humid continental climate with hot summers and no dry season. The area within 25 mi of this station is covered by grasslands (49%), croplands (45%), and lakes and rivers (3%).
The month of December is characterized by falling daily high temperatures, with daily highs decreasing from 36Â°F to 27Â°F over the course of the month, exceeding 50Â°F or dropping below 13Â°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 27 with 9:00 hours of daylight; the longest day is December 1 with 9:14 hours of daylight.
The earliest sunrise is at 7:10am on December 1; the latest sunset is at 4:32pm on December 31; the latest sunrise is at 7:29am on December 31; the earliest sunset is at 4:22pm on December 10.
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 90% (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 34% of the time, partly cloudy 8% of the time, and mostly cloudy or overcast 58% of the time.
The probability that precipitation will be observed at this location varies throughout the month. Precipitation is most likely around December 26, occurring in 62% of days. Precipitation is least likely around December 1, occurring in 56% of days.
Throughout December, the most common forms of precipitation are light snow and moderate snow.
Light snow is the most severe precipitation observed during 58% of those days with precipitation. It is most likely around December 31, when it is observed during 39% of all days.
Moderate snow is the most severe precipitation observed during 14% of those days with precipitation. It is most likely around December 30, when it is observed during 10% of all days.
The likelihood of snow falling is highest around December 30, occurring in 52% of days.
Accumulation at this location in December is likely. The chances of there being snow on the ground are highest around December 31, occurring 71% of the time.
The snow is typically at its deepest on December 13, with a median depth of 3.3"; the depth exceeds 9.3" only one year out of ten.
The relative humidity typically ranges from 62% (mildly humid) to 90% (very humid) over the course of a typical December, rarely dropping below 43% (comfortable) and reaching as high as 100% (very humid).
The air is driest around December 1, at which time the relative humidity drops below 72% (humid) three days out of four; it is most humid around December 5, rising above 85% (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 7Â°F (dry) to 28Â°F (dry) and is rarely below -13Â°F (dry) or above 42Â°F (dry).
Over the course of December typical wind speeds vary from 1 mph to 15 mph (light air to moderate breeze), rarely exceeding 22 mph (fresh breeze).
The highest average wind speed of 9 mph (gentle breeze) occurs around December 1, at which time the average daily maximum wind speed is 15 mph (moderate breeze).
The lowest average wind speed of 9 mph (gentle breeze) occurs around December 13, at which time the average daily maximum wind speed is 15 mph (moderate breeze).