This report describes the typical weather at the Jackson Hole Airport (Jackson Hole, Wyoming, United States) weather station over the course of an average September. It is based on the historical records from 1980 to 2012. Earlier records are either unavailable or unreliable.
Jackson Hole, Wyoming has a humid subarctic continental climate with cool summers and no dry season. The area within 25 mi of this station is covered by forests (85%), croplands (9%), grasslands (4%), and lakes and rivers (2%).
The month of September is characterized by rapidly falling daily high temperatures, with daily highs decreasing from 73°F to 61°F over the course of the month, exceeding 82°F or dropping below 47°F only one day in ten.
Over the course of September, the length of the day is decreasing. From the start to the end of the month, the length of the day decreases by 1:26 hours, implying an average day-over-day decrease of 2.9 minutes.
The shortest day of the month is September 30 with 11:44 hours of daylight; the longest day is September 1 with 13:10 hours of daylight.
The earliest sunrise is at 6:48am on September 1; the latest sunset is at 7:58pm on September 1; the latest sunrise is at 7:20am on September 30; the earliest sunset is at 7:04pm on September 30.
Daylight savings time is observed in 2012 but it neither starts nor ends in September, so the entire month is in daylight time.
The median cloud cover ranges from 13% (mostly clear) to 25% (mostly clear). The trend is for the sky to be becoming cloudier with the median cloud cover increasing by 12% from the start to the end of the month.
On September 1, the clearest day of the month, the sky is clear, mostly clear, or partly cloudy 54% of the time, and overcast or mostly cloudy 21% of the time.
On September 30, the cloudiest day of the month, the sky is overcast, mostly cloudy, or partly cloudy 33% of the time, and clear or mostly clear 45% of the time.
The average probability that some form of precipitation will be observed in a given day is 17%, with little variation over the course of the month.
Throughout September, the most common forms of precipitation are thunderstorms, light rain, and light snow.
Thunderstorms are the most severe precipitation observed during 44% of those days with precipitation. They are most likely around September 1, when it is observed during 11% of all days.
Light rain is the most severe precipitation observed during 34% of those days with precipitation. It is most likely around September 12, when it is observed during 6% of all days.
Light snow is the most severe precipitation observed during 14% of those days with precipitation. It is most likely around September 30, when it is observed during 4% of all days.
The likelihood of snow falling is highest around September 30, occurring in 5% of days.
Either snow rarely accumulates at this location in September or snow depth measurements are unavailable or unreliable.
The relative humidity typically ranges from 26% (dry) to 85% (humid) over the course of a typical September, rarely dropping below 13% (very dry) and reaching as high as 99% (very humid).
The air is driest around September 1, at which time the relative humidity drops below 31% (comfortable) three days out of four; it is most humid around September 28, rising above 77% (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 September, the dew point typically varies from 22°F (dry) to 42°F (dry) and is rarely below 13°F (dry) or above 51°F (very comfortable).
Over the course of September typical wind speeds vary from 0 mph to 14 mph (calm to moderate breeze), rarely exceeding 22 mph (fresh breeze).
The highest average wind speed of 6 mph (light breeze) occurs around September 24, at which time the average daily maximum wind speed is 14 mph (moderate breeze).
The lowest average wind speed of 6 mph (light breeze) occurs around September 5, at which time the average daily maximum wind speed is 14 mph (moderate breeze).