This report describes the typical weather at the Charlottesville-Albemarle Airport (Charlottesville, Virginia, United States) weather station over the course of an average September. It is based on the historical records from 1974 to 2012. Earlier records are either unavailable or unreliable.
Charlottesville, Virginia has a warm humid temperate climate with hot summers and no dry season. The area within 25 mi of this station is covered by forests (99%).
The month of September is characterized by rapidly falling daily high temperatures, with daily highs decreasing from 83Â°F to 73Â°F over the course of the month, exceeding 91Â°F or dropping below 63Â°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 1:10 hours, implying an average day-over-day decrease of 2.3 minutes.
The shortest day of the month is September 30 with 11:49 hours of daylight; the longest day is September 1 with 12:59 hours of daylight.
The earliest sunrise is at 6:44am on September 1; the latest sunset is at 7:43pm on September 1; the latest sunrise is at 7:09am on September 30; the earliest sunset is at 6:58pm 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 42% (partly cloudy) to 50% (partly cloudy). The trend is for the sky to be clearing with the median cloud cover decreasing by 7% from the start to the end of the month.
On September 15, a representative day, the sky is clear or mostly clear 40% of the time, partly cloudy 7% of the time, and mostly cloudy or overcast 38% of the time.
The probability that precipitation will be observed at this location varies throughout the month. Precipitation is most likely around September 1, occurring in 38% of days. Precipitation is least likely around September 21, occurring in 34% of days.
Throughout September, the most common forms of precipitation are light rain, moderate rain, and thunderstorms.
Light rain is the most severe precipitation observed during 37% of those days with precipitation. It is most likely around September 30, when it is observed during 15% of all days.
Moderate rain is the most severe precipitation observed during 27% of those days with precipitation. It is most likely around September 27, when it is observed during 10% of all days.
Thunderstorms are the most severe precipitation observed during 25% of those days with precipitation. They are most likely around September 1, when it is observed during 13% of all days.
Either snow is exceptionally unlikely to fall at this location in September or this station does not reliably report precipitation types.
The relative humidity typically ranges from 51% (mildly humid) to 94% (very humid) over the course of a typical September, rarely dropping below 33% (comfortable) and reaching as high as 100% (very humid).
The air is driest around September 30, at which time the relative humidity drops below 59% (mildly humid) three days out of four; it is most humid around September 1, rising above 92% (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 September, the dew point typically varies from 48Â°F (dry) to 67Â°F (muggy) and is rarely below 35Â°F (dry) or above 73Â°F (very muggy).
The time of the month between September 8 and September 30 is the most comfortable, with dew points that are neither too dry nor too muggy.
Over the course of September typical wind speeds vary from 0 mph to 11 mph (calm to gentle breeze), rarely exceeding 16 mph (moderate breeze).
The highest average wind speed of 5 mph (light breeze) occurs around September 25, 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 September 1, at which time the average daily maximum wind speed is 10 mph (gentle breeze).