This report describes the typical weather at the Phoenix Deer Valley Airport (Phoenix, Arizona, United States) weather station over the course of an average January. It is based on the historical records from 1997 to 2012. Earlier records are either unavailable or unreliable.
Phoenix, Arizona has a hot desert climate. The area within 25 mi of this station is covered by shrublands (86%), grasslands (8%), built-up areas (3%), and croplands (2%).
The month of January is characterized by gradually rising daily high temperatures, with daily highs around 65°F throughout the month, exceeding 74°F or dropping below 55°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 1 with 9:58 hours of daylight; the longest day is January 31 with 10:33 hours of daylight.
The earliest sunrise is at 7:25am on January 31; the latest sunset is at 5:58pm on January 31; the latest sunrise is at 7:34am on January 5; the earliest sunset is at 5:31pm on January 1.
Daylight savings time (DST) is not observed in 2012.
The median cloud cover is 0% (clear) and does not vary substantially over the course of the month.
On January 16, a representative day, the sky is clear or mostly clear 77% of the time, partly cloudy 3% of the time, and mostly cloudy or overcast 15% of the time.
The average probability that some form of precipitation will be observed in a given day is 15%, with little variation over the course of the month.
Throughout January, the most common forms of precipitation are light rain, moderate rain, thunderstorms, and heavy rain.
Light rain is the most severe precipitation observed during 53% of those days with precipitation. It is most likely around January 1, when it is observed during 8% of all days.
Moderate rain is the most severe precipitation observed during 24% of those days with precipitation. It is most likely around January 28, when it is observed during 4% of all days.
Thunderstorms are the most severe precipitation observed during 12% of those days with precipitation. They are most likely around January 29, when it is observed during 3% of all days.
Heavy rain is the most severe precipitation observed during 10% of those days with precipitation. It is most likely around January 24, when it is observed during 2% of all days.
Either snow is exceptionally unlikely to fall at this location in January or this station does not reliably report precipitation types.
The relative humidity typically ranges from 25% (dry) to 61% (mildly humid) over the course of a typical January, rarely dropping below 12% (very dry), or exceeding 88% (very humid).
The air is driest around January 23, at which time the relative humidity drops below 31% (comfortable) three days out of four; it is most humid around January 1, rising above 46% (comfortable) 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 23°F (dry) to 34°F (dry) and is rarely below 10°F (dry) or above 47°F (dry).
Over the course of January typical wind speeds vary from 0 mph to 11 mph (calm to gentle breeze), rarely exceeding 17 mph (moderate breeze).
The highest average wind speed of 5 mph (light breeze) occurs around January 31, at which time the average daily maximum wind speed is 11 mph (gentle breeze).
The lowest average wind speed of 4 mph (light breeze) occurs around January 8, at which time the average daily maximum wind speed is 10 mph (gentle breeze).