This report describes the typical weather at the Zürich Airport (Kloten Airport) (Zürich/Kloten, Switzerland) 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.
Zürich/Kloten has a humid continental climate with warm summers and no dry season. The area within 25 mi of this station is covered by croplands (88%), forests (6%), lakes and rivers (3%), and built-up areas (2%).
The month of September is characterized by falling daily high temperatures, with daily highs decreasing from 71°F to 63°F over the course of the month, exceeding 80°F or dropping below 54°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 1:37 hours, implying an average day-over-day decrease of 3.2 minutes.
The shortest day of the month is September 30 with 11:43 hours of daylight; the longest day is September 1 with 13:20 hours of daylight.
The earliest sunrise is at 6:45am on September 1; the latest sunset is at 8:05pm on September 1; the latest sunrise is at 7:24am on September 30; the earliest sunset is at 7:07pm 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 68% (partly cloudy) to 80% (partly cloudy). 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 51% of the time, and overcast or mostly cloudy 39% of the time.
On September 30, the cloudiest day of the month, the sky is overcast, mostly cloudy, or partly cloudy 66% of the time, and clear or mostly clear 22% of the time.
The average probability that some form of precipitation will be observed in a given day is 49%, with little variation over the course of the month.
Throughout September, the most common forms of precipitation are moderate rain, thunderstorms, and light rain.
Moderate rain is the most severe precipitation observed during 50% of those days with precipitation. It is most likely around September 25, when it is observed during 27% of all days.
Thunderstorms are the most severe precipitation observed during 20% of those days with precipitation. They are most likely around September 1, when it is observed during 14% of all days.
Light rain is the most severe precipitation observed during 17% of those days with precipitation. It is most likely around September 30, when it is observed during 9% 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 53% (mildly humid) to 98% (very humid) over the course of a typical September, rarely dropping below 38% (comfortable) and reaching as high as 100% (very humid).
The air is driest around September 1, at which time the relative humidity drops below 61% (mildly humid) three days out of four; it is most humid around September 26, rising above 96% (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 45°F (dry) to 57°F (comfortable) and is rarely below 37°F (dry) or above 63°F (mildy humid).
The time of the month between September 1 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 10 mph (calm to gentle breeze), rarely exceeding 16 mph (moderate breeze).
The highest average wind speed of 5 mph (light breeze) occurs around September 6, at which time the average daily maximum wind speed is 10 mph (gentle breeze).
The lowest average wind speed of 4 mph (light breeze) occurs around September 25, at which time the average daily maximum wind speed is 9 mph (gentle breeze).