This report describes the typical weather at the Calgary/Springbank Airport (Calgary, Alberta, Canada) weather station over the course of an average September. It is based on the historical records from 1999 to 2012. Earlier records are either unavailable or unreliable.
Calgary, Alberta has a humid continental climate with warm summers and no dry season. The area within 25 mi of this station is covered by forests (70%), croplands (16%), grasslands (7%), and built-up areas (5%).
The month of September is characterized by falling daily high temperatures, with daily highs decreasing from 66°F to 57°F over the course of the month, exceeding 78°F or dropping below 44°F only one day in ten.
Over the course of September, the length of the day is rapidly decreasing. From the start to the end of the month, the length of the day decreases by 1:52 hours, implying an average day-over-day decrease of 3.7 minutes.
The shortest day of the month is September 30 with 11:39 hours of daylight; the longest day is September 1 with 13:31 hours of daylight.
The earliest sunrise is at 6:52am on September 1; the latest sunset is at 8:22pm on September 1; the latest sunrise is at 7:37am on September 30; the earliest sunset is at 7:16pm on September 30.
Daylight saving 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 is 67% (partly cloudy) and does not vary substantially over the course of the month.
On September 15, a representative day, the sky is clear or mostly clear 29% of the time, partly cloudy 7% of the time, and mostly cloudy or overcast 44% of the time.
The probability that precipitation will be observed at this location varies throughout the month. Precipitation is most likely around September 4, occurring in 40% of days. Precipitation is least likely around September 25, occurring in 35% of days.
Throughout September, the most common forms of precipitation are light rain, thunderstorms, and light snow.
Light rain is the most severe precipitation observed during 53% of those days with precipitation. It is most likely around September 7, when it is observed during 21% of all days.
Thunderstorms are the most severe precipitation observed during 16% of those days with precipitation. They are most likely around September 1, when it is observed during 12% of all days.
Light snow is the most severe precipitation observed during 13% of those days with precipitation. It is most likely around September 30, when it is observed during 8% of all days.
The likelihood of snow falling is highest around September 30, occurring in 12% 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 41% (comfortable) to 91% (very humid) over the course of a typical September, rarely dropping below 26% (dry) and reaching as high as 100% (very humid).
The air is driest around September 30, at which time the relative humidity drops below 49% (comfortable) three days out of four; it is most humid around September 9, rising above 86% (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 26°F (dry) to 46°F (dry) and is rarely below 19°F (dry) or above 51°F (very comfortable).
Over the course of September typical wind speeds vary from 0 mph to 15 mph (calm to moderate breeze), rarely exceeding 23 mph (fresh breeze).
The highest average wind speed of 7 mph (light breeze) occurs around September 29, at which time the average daily maximum wind speed is 15 mph (moderate breeze).
The lowest average wind speed of 7 mph (light breeze) occurs around September 25, at which time the average daily maximum wind speed is 14 mph (moderate breeze).