This report describes the typical weather at the South Bend (South Bend, Indiana, 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.
South Bend, Indiana has a humid continental climate with hot summers and no dry season. The area within 25 mi of this station is covered by croplands (73%), forests (16%), built-up areas (4%), oceans and seas (4%), and grasslands (3%).
The month of December is characterized by falling daily high temperatures, with daily highs decreasing from 41°F to 33°F over the course of the month, exceeding 54°F or dropping below 19°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 25 with 9:09 hours of daylight; the longest day is December 1 with 9:23 hours of daylight.
The earliest sunrise is at 7:53am on December 1; the latest sunset is at 5:25pm on December 31; the latest sunrise is at 8:13am on December 31; the earliest sunset is at 5:14pm on December 7.
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 99% (overcast) and does not vary substantially over the course of the month.
On December 16, a representative day, the sky is clear or mostly clear 22% of the time, partly cloudy 8% of the time, and mostly cloudy or overcast 71% of the time.
The probability that precipitation will be observed at this location varies throughout the month. Precipitation is most likely around December 30, occurring in 73% of days. Precipitation is least likely around December 1, occurring in 65% of days.
Throughout December, the most common forms of precipitation are light snow, light rain, and moderate snow.
Light snow is the most severe precipitation observed during 53% of those days with precipitation. It is most likely around December 31, when it is observed during 44% of all days.
Light rain is the most severe precipitation observed during 17% of those days with precipitation. It is most likely around December 1, when it is observed during 15% of all days.
Moderate snow is the most severe precipitation observed during 12% of those days with precipitation. It is most likely around December 31, when it is observed during 10% of all days.
The likelihood of snow falling is highest around December 31, occurring in 57% of days.
Accumulation at this location in December is just more likely than not. The chances of there being snow on the ground are highest around December 31, occurring 59% of the time.
The snow is typically at its deepest on December 31, with a median depth of 3.6"; the depth exceeds 10.4" only one year out of ten.
The relative humidity typically ranges from 63% (mildly humid) to 91% (very humid) over the course of a typical December, rarely dropping below 47% (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 21, rising above 87% (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 15°F (dry) to 33°F (dry) and is rarely below -2°F (dry) or above 48°F (dry).
Over the course of December typical wind speeds vary from 4 mph to 17 mph (light breeze to moderate breeze), rarely exceeding 24 mph (fresh breeze).
The highest average wind speed of 11 mph (gentle breeze) occurs around December 7, at which time the average daily maximum wind speed is 17 mph (moderate breeze).
The lowest average wind speed of 10 mph (gentle breeze) occurs around December 21, at which time the average daily maximum wind speed is 16 mph (moderate breeze).