This report describes the typical weather at the Ann Arbor Municipal Airport (Ann Arbor, Michigan, United States) weather station over the course of an average January. It is based on the historical records from 1999 to 2012. Earlier records are either unavailable or unreliable.
Ann Arbor, Michigan has a humid continental climate with hot summers and no dry season. The area within 25 mi of this station is covered by grasslands (44%), croplands (38%), forests (9%), and built-up areas (8%).
The month of January is characterized by gradually falling daily high temperatures, with daily highs ranging from 34°F to 30°F over the course of the month, exceeding 46°F or dropping below 19°F only one day in ten.
Over the course of January, the length of the day is gradually increasing. From the start to the end of the month, the length of the day increases by 49 minutes, implying an average day-over-day increase of 1.6 minutes.
The shortest day of the month is January 1 with 9:09 hours of daylight; the longest day is January 31 with 9:58 hours of daylight.
The earliest sunrise is at 7:50am on January 31; the latest sunset is at 5:48pm on January 31; the latest sunrise is at 8:04am on January 1; the earliest sunset is at 5:13pm on January 1.
Daylight savings time is observed in 2012 but it neither starts nor ends in January, so the entire month is in standard time.
The median cloud cover ranges from 82% (mostly cloudy) to 92% (mostly cloudy). The trend is for the sky to be clearing with the median cloud cover decreasing by 9% from the start to the end of the month.
On January 16, a representative day, the sky is clear or mostly clear 31% of the time, partly cloudy 3% of the time, and mostly cloudy or overcast 65% of the time.
The probability that precipitation will be observed at this location varies throughout the month. Precipitation is most likely around January 4, occurring in 65% of days. Precipitation is least likely around January 31, occurring in 61% of days.
Throughout January, the most common forms of precipitation are light snow and moderate snow.
Light snow is the most severe precipitation observed during 69% of those days with precipitation. It is most likely around January 11, when it is observed during 45% of all days.
Moderate 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 9% of all days.
The likelihood of snow falling is highest around January 14, occurring in 53% of days.
Either snow rarely accumulates at this location in January or snow depth measurements are unavailable or unreliable.
The relative humidity typically ranges from 62% (mildly humid) to 92% (very humid) over the course of a typical January, rarely dropping below 47% (comfortable) and reaching as high as 99% (very humid).
The air is driest around January 30, at which time the relative humidity drops below 69% (mildly humid) three days out of four; it is most humid around January 2, rising above 88% (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 8°F (dry) to 27°F (dry) and is rarely below -7°F (dry) or above 39°F (dry).
Over the course of January typical wind speeds vary from 1 mph to 15 mph (light air to moderate breeze), rarely exceeding 21 mph (fresh breeze).
The highest average wind speed of 9 mph (gentle breeze) occurs around January 1, at which time the average daily maximum wind speed is 15 mph (moderate breeze).
The lowest average wind speed of 8 mph (gentle breeze) occurs around January 24, at which time the average daily maximum wind speed is 14 mph (moderate breeze).