This report describes the typical weather at the Flagstaff Pulliam Airport (Flagstaff, Arizona, United States) weather station over the course of an average January. It is based on the historical records from 1974 to 2012. Earlier records are either unavailable or unreliable.
Flagstaff, Arizona has a continental climate with dry warm summers. The area within 25 mi of this station is covered by shrublands (93%) and grasslands (6%).
The month of January is characterized by essentially constant daily high temperatures, with daily highs around 42°F throughout the month, exceeding 53°F or dropping below 30°F only one day in ten.
Over the course of January, the length of the day is gradually increasing. The shortest day of the month is January 2 with 9:51 hours of daylight; the longest day is January 31 with 10:27 hours of daylight.
The earliest sunrise is at 7:27am on January 31; the latest sunset is at 5:54pm on January 31; the latest sunrise is at 7:36am on January 7; the earliest sunset is at 5:26pm on January 1.
Daylight savings time (DST) is not observed in 2012.
The median cloud cover ranges from 17% (mostly clear) to 25% (mostly clear). The trend is for the sky to be becoming cloudier with the median cloud cover increasing by 8% from the start to the end of the month.
On January 16, a representative day, the sky is clear or mostly clear 47% of the time, partly cloudy 9% of the time, and mostly cloudy or overcast 29% of the time.
The average probability that some form of precipitation will be observed in a given day is 32%, with little variation over the course of the month.
Throughout January, the most common forms of precipitation are light snow and moderate snow.
Light snow is the most severe precipitation observed during 66% of those days with precipitation. It is most likely around January 19, when it is observed during 22% of all days.
Moderate snow is the most severe precipitation observed during 20% of those days with precipitation. It is most likely around January 17, when it is observed during 7% of all days.
The likelihood of snow falling is highest around January 19, occurring in 29% of days.
Accumulation at this location in January is unlikely. The chances of there being snow on the ground are highest around January 30, occurring 20% of the time.
The snow is typically at its deepest on January 21, with a median depth of 7.9"; the depth exceeds 18.4" only one year out of ten.
The relative humidity typically ranges from 39% (comfortable) to 87% (very humid) over the course of a typical January, rarely dropping below 18% (dry) and reaching as high as 100% (very humid).
The air is driest around January 28, at which time the relative humidity drops below 49% (comfortable) three days out of four; it is most humid around January 30, rising above 80% (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 9°F (dry) to 23°F (dry) and is rarely below -5°F (dry) or above 33°F (dry).
Over the course of January typical wind speeds vary from 0 mph to 13 mph (calm to moderate breeze), rarely exceeding 21 mph (fresh breeze).
The highest average wind speed of 6 mph (light breeze) occurs around January 31, at which time the average daily maximum wind speed is 13 mph (moderate breeze).
The lowest average wind speed of 6 mph (light breeze) occurs around January 5, at which time the average daily maximum wind speed is 12 mph (gentle breeze).