This report describes the typical weather at the Penticton Regional Airport (South Okanagan Airport) (Penticton, British Columbia, Canada) weather station over the course of an average September. It is based on the historical records from 1977 to 2012. Earlier records are either unavailable or unreliable.
Penticton, British Columbia has a cold semi-arid steppe climate. The area within 25 mi of this station is covered by forests (88%), grasslands (7%), and lakes and rivers (4%).
The month of September is characterized by rapidly falling daily high temperatures, with daily highs decreasing from 76°F to 65°F over the course of the month, exceeding 84°F or dropping below 57°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 1:45 hours, implying an average day-over-day decrease of 3.5 minutes.
The shortest day of the month is September 30 with 11:40 hours of daylight; the longest day is September 1 with 13:26 hours of daylight.
The earliest sunrise is at 6:15am on September 1; the latest sunset is at 7:40pm on September 1; the latest sunrise is at 6:58am on September 30; the earliest sunset is at 6:38pm 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 51% (partly cloudy) to 69% (partly cloudy). The trend is for the sky to be becoming rapidly cloudier with the median cloud cover increasing by 18% 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 58% of the time, and overcast or mostly cloudy 41% of the time.
On September 30, the cloudiest day of the month, the sky is overcast, mostly cloudy, or partly cloudy 61% of the time, and clear or mostly clear 38% of the time.
The probability that precipitation will be observed at this location varies throughout the month. Precipitation is most likely around September 30, occurring in 34% of days. Precipitation is least likely around September 1, occurring in 30% 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 62% of those days with precipitation. It is most likely around September 30, when it is observed during 23% of all days.
Moderate rain is the most severe precipitation observed during 22% of those days with precipitation. It is most likely around September 28, when it is observed during 8% 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 7% 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 35% (comfortable) to 82% (humid) over the course of a typical September, rarely dropping below 24% (dry) and reaching as high as 97% (very humid).
The air is driest around September 1, at which time the relative humidity drops below 40% (comfortable) three days out of four; it is most humid around September 27, rising above 74% (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 34°F (dry) to 52°F (very comfortable) and is rarely below 25°F (dry) or above 58°F (comfortable).
Over the course of September typical wind speeds vary from 0 mph to 12 mph (calm to moderate breeze), rarely exceeding 20 mph (fresh breeze).
The highest average wind speed of 6 mph (light breeze) occurs around September 30, at which time the average daily maximum wind speed is 12 mph (moderate breeze).
The lowest average wind speed of 5 mph (light breeze) occurs around September 5, at which time the average daily maximum wind speed is 12 mph (gentle breeze).